Quite a mystery to me, Jeff. Sounds like you're using the same arrows with both the longbow and recurve limbs. Possibly you could tweak a little there to get arrows that are better optimized for each set of limbs, but for our purposes here, it removes one variable.
I've found from my own experience with the fixed crawl that 5/8” would be in the normal range to get a 20 yard point on. I can understand why you would lower the nock point, just as an experiment, to see if that would raise the p.o.i., but I would guess that a nock point less than 1/2” would be suboptimal as far as arrow flight goes. I would guess that your optimum nock point would be 1/2” or higher.
Really, a point on of 20 yards is ideal for hunting, forget the fixed crawl. However, I’m thinking, as you probably are, that something isn't right for any bow in that pound range to have a natural point on of 20 yards. A 20 yard point on could be achieved with super heavy or super long arrows, but then it would be affecting your recurve as well. It would be nice to have a speed comparison between the longbow and recurve limbs, to find out if something is making the longbow limbs slower than the recurve limbs for some reason. It appears everything you have is good quality, but I suppose the longbow limbs could possibly have some kind of defect. Is there any difference in noise between the longbow and recurve limbs?
As you can see, I'm kind of grasping at straws here.