Actually the denim you should use would be marked "PFD". That indicates "prepared for dying".
I have seen it in yardage, but not in finished jeans.
Some of the DIYers here might have suggestions as to preparing the jean for dyeing.
one thing for sure is, do not try dying if it has not been washed at least two times.
Even if it made junk for everyone else. If it made great garment for you, its a quality shop just for you.If it made a quality garment for everyone else. But made junk for you. then its your junk shop.You need to try it to know.it. Test drive before you buy. sorry, you cant test drive this.In this case you have to buy first, in order to test.
The only way to check the sleeve pitch is to see the coat on you.
Try this, with no shirt on stand side ways in front of a mirror.
Allow your arm to hang down normally and relaxed. This would be your normal sleeve pitch.
Now move your arm forward a couple of inches then back a couple.
Take that distance front to back, and divide it into 1/4" increments.
You can see how many different sleeve pitches there are on the average. There can be more.
The body posture...