I know that the armor class penalty applies to dexterity rolls on skills like tumble, as well as weapon-finesse melee weapon to-hit rolls. Does armor class penalty also apply to the to-hit on ranged attacks, since they are dexterity-based? The manual does not cover this.
I believe you only suffer your armor class penalty to your hit rolls if you are not proficient with your armor, in which case, yes. It would apply to attacks of any kind.
Click on the icon for combat details and check the highlighted blue words. If an attack hits (or misses) it will give the details of all the pluses and minuses that went into the attack...
The max DEX bonus of an armor has more effect on your ranged to-hit attack bonus than anything else might, although as stated your profiencency plays a major roll also. The armor check is taken into account when rolling a CHECK, for instance when you roll a reflex save, or as you said a tumble. A good example is a dark wood buckler, it has a 0 armor check penalty, but still applies a -1 to your to-hit with a two handed weapon.
I think we need to investigate this next time we have a chance to look at the die roll while wearing a DEX limiting armor. You very well may be correct.
In the pnp, at least, the max dex bonus for your worn armor applies only to armor class and nothing else.