And what if my characters don't want to murder folks...?

One of my characters is very benevolent; the other will generally do the right thing (e.g., not murder someone) but could care less about being the "nice guy" or helping everyone (at his own expense). They argue. I wish that they could somehow offer the same XP for all role play choices, but there's no perfect solution to satisfy everyone, I guess. This (quest conclusion) happened to be an occasion wherein my benevolent character would've opted to not lie and thus miss out on the extra XP.

This is a minor concern, I guess, but I am curious to know if they do "all of the quests" are there one or more sets of choices such that they will not be able to reach the highest level.

I'm going to play it out, regardless, but I hope that's not the case. My characters are not shying away from fights...