Thanks for the help.
I realized I had to change Steepness to a non-constant variable and that allowed me to tinker with things. I also moved touch controls way up (rather than directly above event 10 like I was previously doing for some reason) and construct doesn't give me any errors or issues. So it seems I'm making some sort of progress.
A neat thing I noticed is that adding platform behavior allowed the player to stay grounded on beziers (apart from control input) but it negated the effects of setting/changing ax/ay/vx/vy (making changes only granted a temporary burst of speed) and also only allowed 1 jump when simulating jump controls. Does this mean I'll be unable to have consistent jump control over the player so long as I've added the platform behavior?
I also noticed some odd behavior with the player lagging behind the middle sprite instance, but setting x to sprite.x seems to have solved that issue.
What I'm trying to figure out now is if there's a way to specifically set the player's fall speed without messing with everything else. Is that doable?
Lastly, I was wondering, in addition to modifying the Steepness, is there any way to actually pause the formation of beziers altogether?
Thanks again for taking the time to help and pointing me in the right direction