I bought a suit a couple of years ago and ended up getting a 40L jacket. I just tired it on and it's definitely roomy around chest and waist, though, I can't remember why I had to move up a size. I'm guessing it was because my shoulders were too wide for 38. My sleeve length is 34/35; I'm not sure that's proportionate to my height.
Yes, that is proportionate to your height. I will get one of my pea coats out tomorrow and measure it to see what sleeve length you might need.
You need to post a picture. Navy regulations state the sleeve length should be 3/4 of the distance from the wrist joint to the knuckles. In my opinion, an inch shorter than that is still a good fit.