A Few Questions From a Newb

[Finalgenesis]

Hi and welcome~

blood lvl 9 contains all the best mass demon summons, devils are one of them.

For site search, there's a remote search spell for every spell path sprinkled in lvl 2-3 spells over various schools (thau 2, conj 2/3?, evo 2...etc). There's also Voice of tiamat which search all 4 elemental path in water (conj 4), and acashic record that search every path in a province but has a very very high cost (not recommended in most cases).

no to resource =P not quick or reliably at least, there's events but don't count on it. prod scales is really the only way to do it.

Demon lords are so-so to niche, usually they are summoned for something other then SC purpose, they fit more as major caster / support and each usually comes with something special. One can corrupt, one gets free blood slaves, one starts the battle with storm (not sure on this), and one starts battle with heat from hell, most or all of them does something bad to the province they are in every turn I think, like unrest, disease, losing dominion ...etc.

[Olive]

You can increase production by casting Riches from Beneath. Never used it, so I can't tell if it's efficient.