This mod is incredibly fun and fixes a lot of the problems I have with srb2 by adding more depth and providing a wider set of options to the player. Despite my initial criticisms of the momentum thok from SADC, this ability really has nice synergy when paired with the rest of this mod's physics. Unfortunately, srb2's level design is a bit too cramped to make use of the extreme speed capable with XMomentum's trick system. Because of that, perhaps the speed gained with tricks and the momentum thok is too much.
The "thok goes down but up" bit is actually a really valid criticism - let me explain. In order to jumpthok, you need to hold down the jump button for a bit during the thok. Since the thok's horizontal boost responds instantly, there is a noticeable period after the thok begins but before the vertical boost is applied. Once you see it, you can't unsee it. It just looks kinda delayed / janky.
One last thing I should mention is that the trick system looks a bit odd because it uses rollangle combined with directionchar - for example, if I'm doing tricks while moving to the left, my character might be facing to the right since they're upside-down. What I'd suggest is making the player's drawangle spin rapidly once trick mode is enabled.
Great job overall, and I hope some of the design philosophies here (giving the player actions to do after using a spring or running off a slope, adding proper slope momentum, making character movesets deeper) will influence the way 2.3 plays.