Attack Speed was dependant on which refresh rate you were using (30FPS/60FPS) and Scepter of Time. Not sure if that's still the case.
Luck goes up to 80% chance of success, as dependent upon initial Luck. For example, something with 8% odds to succeed can take 1000% Luck before any more luck becomes wasted. Something with 40% odds to succeed can take 200% Luck before any more luck becomes wasted.
Exp has no limit. You can continue to gain experience after a tower reaches level 99, but it will have no effect on the tower.
No limit. Going to incredibly high levels is useful only with Blofeld Satellite System, Muli the Evil Twin or to complete the American Dream quest.
Again, no limit. Practical limit seems to taper off around 1500% or so, where a tower will earn a few Rare items every single level.

THX romeo.
I only want to point out that 100% luck is enough for 40 Prof Chance. because it only represents the additional chance.Same AS 900 would be enough for 8%.

"I only want to point out that 100% luck is enough for 40 Prof Chance. because it only represents the additional chance.Same AS 900 would be enough for 8%."
Right! I kept forgetting the "base 100%" that basic math would dictate. D'oh! =P