Astral Spells/Levels/Boosters

[JonBrave]

Sigh... here goes: sorry if the information is already published across a number of threads, but I'm hoping for a summary....

Since I'm Arco/Astral in my current, I would like to know. Which spells do/don'y my boosters count for?

I (think I) know that, for example, if I "Magic Duel" any boosters (items, cast-spells-raising-levels, ...) I have are ignored, it's just my base Astral and his that competes. Does this apply to all Astral spells? Mind Burn/Paralyze/Soul Slay etc.? Is it that anything which says "Magic Resistance Negates" means no boosters [I don't think so]??

I assume (taken for granted) that any booster levels do help with any fatigue-caused/level-required in order to actually cast these spells.

And where does (or doesn't) my "Spell Focus" amulet come into any of these?

Thanks!