Someone like @Despos would be the best guy to answer a question like this with any real authority. Chris, you there?
It's proportional that way. It's like... a normal sized hat looks tiny on Shaq. Shia is not, afaik, a very big guy, so the opposite holds. 3.5" is pretty standard. In any case, I would definitely listen to @David Reeves, who is a tailor by trade and owns a company that specializes in suiting.
A 37 is not a very large size.
I just looked up Shia's size, and apparently, is is 5'9" and about 155 lbs. That would put him at about a size 38. For context, I am 5'11", and when I weighed 155 lbs, I wore a size 38.
It seems pretty clear that you want large lapels. I would just go for it. 3.5 is standard for "normal" wide lapels, but if you want to be sure to get a larger lapel, go for the 3.75" and do a half notch, as recommended by @David Reeves. Are you working with a tailor, or are you doing this with a MTM program where you can't get great advice? If you are doing this with a tailor, go ahead and bring the picture in, and a good tailor will be able to cut a jacket so that you can get a similar look.
It's not a term I typically hear, but if you get a very slim lapeled suit, you'll often see a very small notch that has a very sharp horizontal "V". I've heard tailors refer to this as a "fishmouth" lapel because of the appearance. I would guess that the half notch lapel is somewhere between the nearly symmetrical V that you see on most notched lapel suits, and the fishmouth lapel.
That said, with an outfit like Black Lapel, I would doubt that they would offer that level of customization.
It seems that you have very specific desires. I don't know where you are located, but if you are anywhere near NYC, you might wish to consider going to Mr Ned's (http://mrnednyc.com/), with a picture of what you want. Vahram is an old school clothier (Wes Anderson reputedly gets his suits made here), and he'll tell you what's what and what is possible, without much fanfare, but that is probably your best chance of getting exactly what you want. Also, for hands on service, and a great deal of expertise, you are not going to get a much better price than he offers ($950).