Spell casting math problems, Can someone explain in "dummy way" Options

[Traks]

Daaamn. I have read sourcebook and other sources, but I still do not get how exactly this is handled. My thoughts so far (which are surely wrong):

You choose spell, Manabolt
You select force of spell, say 6 (my players are quite new and thus have no more than power 6)

You use Sorcery active skill and sorcery pool to cast it?
How damage scales up? Does it for attacking spells?
Does force 6 means enemy will have 6 boxes damaged, so it is 6S?
Protective spells are more understandable this way, number of successes usually means how good you used it.
Except Impr Invis and Invis, is it contest (you reroll till get one, highest number and enemies later use this number as target) or you just use number of successes to later evaluate this?

For drain, you use Body + Spellpool again?
How much is drain? Those +1 +M or other numbers cofuse me somehow.
I just do not get how exactly this calculates, for the same Manabolt