I don't think there's any limit on Global spells. If so, I haven't hit it.
The Diabolical Faith dominion theme is, I believe, a Marignon theme. It postulates that the Inquisition failed to contain the heretical Ermor necromancers, and so made a pact with forces powerful enough to counter them: demons. They turned back the Death mages with the "aid" of their new partners/masters, but their faith was tainted. Demon worship is a potent force in a Diabolical Faith Marignon.
I'd have to double-check, but I believe the Demon Jesters are summoned via a Blood magic spell that will be available to anybody who does the research (and has the Juju).
Heart Companions are the sacred guardians of the Arcosephalean Priestesses. They are rough, tough, and expensive. Pretty cool though.
Don't know about Panzuzu. I think the "growing army" is what Johan just mentioned: auto-recruiting for Belphegor.
Shadow Bolt is a ranged spell that bypasses armor and has an area-effect paralysis effect on top of the direct damage it deals to a single target. I believe it is Death magic.
Oh, and BTW, good call on the Assimilation --> Imprint Souls, IMHO. MUCH cooler name.
