cipher - Finding Detective Jack!

I am Aidan and I am a detective. I am in a country I have never visited before. Jack and I have been working on a task for a few days now. We have been very successful in solving a murder mystery which took place a few days back. Our success has unfortunately been bad eyed by a group of criminals who have been following us throughout our investigation. We are sure they have something to do with this murder.

Last night, while we were finalizing our work in our hotel room, there was a thud on the door. And then, the thuds were turned into bangs. After a while, we started hearing the guns firing across the lobby. I asked Jack to take the back door and run. While I was collecting the notes of our investigations in a hurry, I saw Jack disappearing through the back door. I got up and jumped through the window.

I ran without looking back until I came across a crowded street and took a sigh of relief. I had no clue where Jack took off. I wanted to find him in this huge country and I had no idea of how I am going to get in touch with him. There was a restaurant nearby. I went in and ordered coffee. In a few minutes, I finished it up and got my wallet out to pay the bill.

As soon as I took out my wallet, a note came out through my jacket as well. I knew, it was from Jack. Probably, he was showing me a way to get to him. He had this habit of playing with steganography and ciphers. I peeked a little at the note but didn't understood it. Probably, I needed a peaceful place to sit and think. Hence, I took off in search of a new place to stay. I looked for another hotel. Didn't took much long. I found it. I booked a room and went in.

I ordered a cup of coffee to get my brain ready to travel through this mystery of a note and opened it. The note looked like this -

I have the text version of the complete note as well.

       
 -----------------           -------------------------------------------------
 |a b c D        |           |iyst iaywx bwv bnbv gwzm xj xjqgl pkzqvfc fqgl.| 
 |where a gives 4|           |ykgrd cizm cyms wca wvxogvdxfjtjr -            |
 |b gives 6 and  |     ----> |(rbiaf ugn clnifpn wtg zqiczip rgjebqu tpjav   |
 |c gives 4 and  |           |boh cafrfda deutpifpn xx ehHH SR EI)           |

 |d gives 6.     |           -------------------------------------------------
 -----------------                         |
                                           |
                                           V
------------------------------------------------------------------------------------
| Aidan, the key for the following part is hidden up there. All you need to do is, |
|go west with what you've got. Vigenère will be your way through.                  |
------------------------------------------------------------------------------------
                                           |
                                           |

                                           V
-----------------------------------------------------------------------------------------
| R izwazx ppy xkbp lrdr isjtw roh axxsyv.Chqc kwirl pzdf oirrdury fsls gytug vv oidwl  |
|wvzpvzmz. Opfxmbeff qv bkrbogg wqey Eakee.Ulv efhgha wupd nieupp zvwqh. Memxz dmcm     |
|hzoffg dfak. Tdlejf gfff oirrdury alv dmivvznu cuzrws. Ekuidiu hb mxiz qw. Hvijzv lpca.|
|Zjifmfn!                                                                               |
-----------------------------------------------------------------------------------------
                                           ^
                                           |
                                           |

---------------------------------------------------------------
|Once you have the above note, this riddle will help you out -|     
|                                                             |    
|    Swiftly you begin digging the note.                      |
|    Lock a couple, and eye the brave!                        |
|    The brave shall take you ahead.                          |
|    Girth of which, offers what you crave!                   |
---------------------------------------------------------------

For efficient copy-pasting the stuff use this -

iyst iaywx bwv bnbv gwzm xj xjqgl pkzqvfc fqgl. ykgrd cizm cyms wca wvxogvdxfjtjr - (rbiaf ugn clnifpn wtg zqiczip rgjebqu tpjav boh cafrfda deutpifpn xx eh HH SR EI)

a b c D
where a gives 4
b gives 6 and
c gives 4 and
d gives 6.

Aidan, the key for the following part is hidden up there. All you need to do is, go west with what you've got. Vigenère will be your way through.

R izwazx ppy xkbp lrdr isjtw roh axxsyv.Chqc kwirl pzdf oirrdury fsls gytug vv oidwl wvzpvzmz. Opfxmbeff qv bkrbogg wqey Eakee.Ulv efhgha wupd nieupp zvwqh. Memxz dmcm hzoffg dfak. Tdlejf gfff oirrdury alv dmivvznu cuzrws. Ekuidiu hb mxiz qw. Hvijzv lpca. Zjifmfn!

Once you have the above note, this riddle will help you out -
Swiftly you begin digging the note.

Lock a couple, and eye the brave!
The brave shall take you ahead.
Girth of which, offers what you crave!

Can you help me find Jack?

UPDATE

It's been days now. Jack might be waiting for me. It's getting really tough to break the cipher for me. I went to our hotel last night for checking if I can get any help in there. Any clue will help. But, I didn't found much except a piece of paper which had this -

Seek for the dark, the tall, the stroked and the ones which bend.
Seek in the gibberish you have at the top.

Keys are lost in that mess my friend.
Use them to clean that awful looking block.

I turned the note and there were more lines -

4 keys for the 4 words needless to say,
Word sizes are already in there.
Find them and follow their trail,
Approach the right direction with care.

Hint 1 for Block 2

The riddle tells you on how to solve the block 2. Lock a couple could mean lock a couple of words. You can now guess what is brave and girth..Well its just what it is. :-)

Hint 2 for Block 2

Here's a way of solving note 2 with an example

His behavior of yelling is illusion. It always has proof. $\rightarrow$ HELLO

Answer

This is a community wiki answer which serves as a collection of things solved brilliantly by Gareth and M Oehm

Detective Jack is -

WAITING AT THE AIRPORT!

a b c D
where a gives 4
b gives 6 and
c gives 4 and
d gives 6.

This block tells us that we need to find the bold,italic,strike through and capital letters from the block one and apply them as key to the same block which will give word of length n. Where n is mentioned as 4,6,4,6

We have..

Bold as pyi
Italics as wqpqx
Strike Through as dheh
Capital as hhsrei

Applying these as keys to block one we get -
pyi - take ksjyp myn mptg ioko pu zbbid amrbxxn hirn. qvijo eako ujok hes hxpzinozxuvbc - (tttcx fif nnfthhy ylr bitertr jrlwmsm erblx tzj ulhjqfs ogmeraqrf iz ws JZ DT WT)

wqpqx - midd leihh eaf mxez qhjp bt ittkv aucufqm iuqw. inkbo mldw nipw gnk zzhzqyhhqtwnb - (cllep fqq gvysitx hdj datmcmz cqmilbe wttlf esr nkivpok gieezljzy ha ir SR VV OT)

dheh - from ftupu uso ygxo dpvf uc tcnzh ihsmocv bjde. uddkz vfsi vvfo pzt souhcoaqbcqcn - (kybwy rzj vigeymg smd smbzsei ozfxyjq mmcwo yhd vxynyat zxrmlbcij qu xd AE LN XF)

brac esrpf ksn ugje cosf fs tbjzt ygrjonl bize. gtcjw vqii urfa fys pofxcnwqnspbk - (kjrwx nzv lhfbyxw slz syryrbi zpfwujc clbto jxd utyzozs wxcclayiv gt wa AP BN WB)

TAKE MIDDLE FROM BRACES

So, taking middle from the braces "()" we get

iyst iaywx bwv bnbv gwzm xj xjqgl pkzqvfc fqgl. ykgrd cizm cyms wca wvxogvdxfjtjr - (rbiaf ugn clnifpn wtg zqiczip rgjebqu tpjav boh cafrfda deutpifpn xx eh HH SR EI)

The note tells us to go west with what we get hence reversing it gives -

PROJECT IGI

Applying this as key to block 1 gives -

the key for the next note is james herbert bond. scrap text used for steganography - (jvalo gxj asfcxaw ikc xxawrty dxfciio lasmm xmo uuxcopr zcbljaqyz ot co ZB KC NU)

R izwazx ppy xkbp lrdr isjtw roh axxsyv.Chqc kwirl pzdf oirrdury fsls gytug vv oidwl wvzpvzmz. Opfxmbeff qv bkrbogg wqey Eakee.Ulv efhgha wupd nieupp zvwqh. Memxz dmcm hzoffg dfak. Tdlejf gfff oirrdury alv dmivvznu cuzrws. Ekuidiu hb mxiz qw. Hvijzv lpca. Zjifmfn!

Now that we have the key for this block. Applying it gives -

I insist you grab your worms and jewels.They speak like avoiding your chats is first priority. Accompany me against them Aidan.The letter will gently guide. Death will divert away. Please come avoiding the circular tunnel. Attempt to join me. Arrive soon. Waiting!

Swiftly you begin digging the note.
Lock a couple, and eye the brave!
The brave shall take you ahead.
Girth of which, offers what you crave!

This final riddle tells us to lock a couple of words and look at the brave i.e. first word. Girth or size of which will take us ahead.

I insist you grab your worms and jewels.They speak like avoiding your chats is first priority. Accompany me against them Aidan.The letter will gently guide. Death will divert away. Please come avoiding the circular tunnel. Attempt to join me. Arrive soon. Waiting!

So, taking the nth letter from second word of every pair based on the length of first word we get -

I AM WAITING AT THE AIRPORT!