Summoners don't really use lots of magic power, mostly because the verses magic has very limited uses. The summoning ceremony in particular has a 100% sucess rate. It's designed so that all kinds of high level mythological beings, like the red lady, can't interfere with it.
And her power is more a divine authority than magic. It's a consequence of her existence as god, much like people having a set lifespan is the consequence of the existence of a god of death, and its effect borrows elements of the summoning ceremony. I don't think it would fail by chance.
Huh. Not much Amane can do here especially if she summons and brings out a tier 4 god with resistence to his powers at least when unfocused. Maybe if he focused Nameless Glory into dark aura but he only does that when extremely angered to the point of wanting to kill in horrible ways.
Yes, he does, but she can apparently deal with it, cus her magic cannot be affected by probability, and the fate would just make things go his way but since white queen would join the field RIP. So it mostly makes you make mistakes. His in most in character fate stuff is death hax (heart stop) but she has type 2. But it's mostly due to the fact that Amane can't stop her magic.