a) The minor campaign is the same as the Grand Campaign, the problem is that if you play through the RTW.exe that I screwed it a bit so it doesn't work in 0.34; you could also install 0.34a and play with that.
b) Small attack values just make a lower killing speed, and if all units have low attack values it doesn't change anything else really.
c) You can mod the muslims in but they don't have a tech-tree or something yet.