Thank you for the response!

"my_height" is distance to ground, which I get from "c_trace" and lowest point of the BBOX:
vec_set(vecFrom, my.x);
vec_set(vecTo, my.x);
vecTo.z -= 4000;
c_trace(vecFrom, vecTo, trace_mode);
// get lowest point of BBOX:
vec_for_min(temp_vec, my);
// get distance to ground:
my_height = my.z + temp_vec.z - target.z;
I mostly use variables (such as "my_heigh" etc). But I didn't understand your last question, sorry for my English man.
If you asked what framerate (fps_max) am I aiming for, then I'd say "60"

If I don't limit, I get stable 512 fps and jumping behavior.
Edit: BTW, thank you! I guess you were right! When I changed "-10" into positive value in this line:
absdist.z = -maxv(my_height, -10 * time_step);
Jumping problem disappeared!

But now, movement on slopes isn't smooth (it's almost smooth, jerking a little bit).
When I limit max fps by 60, it's very smooth (as it was before changes) on slopes!

But still if I try it with 512, it isn't.
EDIT2: I've increased that positive value from 10 into 100, and it's smooth now

But I need to test it. Maybe that will affect on something...
Math was always my weak point..

Thank you once again my friend! I appreciate it!
EDIT3: I've found what was causing those little jerking stuff on slopes!

That wasn't gravity stuff (I fixed it completely with your help)!!
Problem was with camera Z smoothing script, but it works perfect now!

Thanks once again!!!