[Radek]

1. I don't know. But if Morrowind follows Arena and Daggerfall history then:

a) Spell Absorption (checked first)
b) Spell Reflection
c) Spell Resistance (checked last).

In fact, both in Arena and Daggerfall was also (d) Natural Spell Absorption as the last resort for sorcerors but Morrowind uses some strange rules for "stacking" resistance effects so that the natural spell absorption of a sorceror seems to be stacked with acquired spell absorption. It's unlogical. These effect should not stack.

2. Nothing can be usually done. The resistances are almost always abilities, that means, they never expire, they cannot be dispelled, and they are active all the time without need of casting them. Only sometimes, the resistance are really cast by a monster.