Look, if you want to use a skill check to do damage you should compare to Maneuvers that do the same thing. Diamond Mind maneuvers lets you use concentration checks for things, including a higher level one where you deal extra damage equal to the check times four. Granted, its a lot harder to boost Concentration than Jump, but this isn't a terrible starting point.

I suggest not increasing/multiplying your speed at all, but allowing the jump checks to scale how they will. Yeah, maybe fast movement, but specify if its an Enhancement bonus to speed or not, as multiple bonuses of the same type do not stack. Besides, being able to charge further doesn't increase your movement speed for jump checks. I think Cheetahs can charge x8 move speed 1/minute or something, and they don't get a bonus to jump checks while doing so.

It'll still make for large jump checks, but it won't scale in strange ways. Somewhere at the beginning add half the jump check, then increase to full jump check, then x2 at the upper end.