OP, first of all, I think your first mistake is wasting time with S&D. When I read your line where you say that you develop splits from wearing your hair in even a braid-out, it made no sense to me. I can see splits from heat, but what I think is happening is when your hair is stretched you are seeing the splits the futile task of S&D didn't get out. Also when you S&D you end up leaving hairs that have already split and torn away because they do not look split. They are damaged beyond just being split so you leave them there and they end up causing you problems.
So my suggestion is to put all your hair in small braids and snip a TINY amount from all your braids every couple of months. So tiny that you don't even miss it. You will be surprised at how much better your hair will do and how less time you will spend looking for splits.
Secondly, there are a few MBL or thereabouts naturals (Mwedzi, Virtuenow...come to mind) who wear their hair stretched all the time. They could probably shed some light on how they achieve that and how they are able to keep splits/knots at bay.
Perhaps you should try stretching your hair using less watery products so there's no curling back on your strands. But this will work best if your ends are in good shape, which IMO is very hard to determine if you're relying on your eyes to tell you which strands are split and which ones are not. As these images show, just because you don't see a split doesn't mean the split didn't happen. The pointed end of my hair in the first image shows the "after-results" of a split. If I were just looking for a fork shape, I'd leave that hair there and it'd continue to weaken the rest of the strand: