I would agree that recovering 6th level slots is a bit much. Similarly, expending 9 slots to maintain concentration seems very weak. Maybe allow the wizard to expend slots with a combined size equal to the level of the spell? Ex: expend one 3rd level, two 2nd level, and two 1st level slots to maintain concentration on a 9th level spell.

I actually like the resistance to nonmagical cold. It feels appropriate that an eldritch horror would grant resistance to natural cold (the far north, deep waters, and air conditioning) but not their own powers. Blanket cold resistance for a 1 level dip also seems a bit much. I would also add a maximum volume for Voidspace, to avoid cheese.

"Mega Corporation" would probably fit better as "Miser" or "Financier" in most settings. I think most of it is fine (if Bankruptcy Policy is meant for 14th level) but the prices for the 1st level features are probably too steep by an order of magnitude. Granting Infusions seems fine, although maybe you could say they are chosen instead of an invocation.