Mission Editor resources:
A) Quick Help. Start here. This will get you familiarized with UA.
B) mission editing.txt: this has a bunch of tips for doing things like AI control, AI FOs and so on.
C) CoC_Arty_Documentation: this is the master list of everything. It's a little daunting, but if you go to the function section, maybe it'll be a little clearer.
You can also UnPbo the tutorial missions.
UA02, UA04, UA05 and UA06 each have enemy fire control systems of varying complexity.
UA06 has an observer system.
And you can post to the coc forums with specific problems.
And I"ll probably kick up some templates in a while.
MLRS airbursts a bunch of DPICM bomblets, yes.
We made a design decision with the UA that each MLRS unit be commanded separately. This is largely because the limitations of OFP make one MLRS plenty powerful. Other reasons are that A) MLRS batteries tend to be dispersed over a 3km by 3km area of operations. B) a fire mission from such batteries would usually involve separate aimpoints for each launcher, and probably multiple aimpoints. Even if B isn't the case IRL, the UA MLRS has enough accuracy that it's necessary.
Still, you can put three MLRS units on the map, set up AMC fire missions and launch them all at once.