To be fair we did try to find aghilies if my memory serves its just that we kind of as you said only tried once, conventionally.
Obviously, we need to do better going forward. Point made that we've made some bad first impressions in a lot of places.
With the scouts, I think I made the mistake of thinking they ran into Sep Stalkers or other automata, which isn't a guarantee of tomb kings actually being active per say.
On that note I regret not chasing the Djin Callers harder to be honest, its mostly been that there have been so many other closer more activley agressive threats present that it seemed counterproductive.
To be fair, there wasn't necessarily things you could have done about these issues. The Scouts probably did indeed run into the automated defences rather than anything specific. I'm not 'blaming' you necessarily, but you can see how people in universe would. For example you didn't have any indicationt that Aghilies was anything other than a particularly capable mortal leader. The specifics of his connections with the Djinncallers and the Skaven were unknown to you, as was his last resort of waking up Settra.
And yes, you have to prioritise stuff, that's true too. However, in general things will indeed get worse the longer you leave them. You might be ok with that as voters, but it's something to consider. You haven't actually looked for the Djinncallers really yet, so you don't know where they've gone, and you also haven't really gotten involved in the Arabyan refugee crisis.
how does Chaos 'work' in this quest canon?
Bascially iss chaos fueled more by mundane actions? Or is chaos fueled more by by active worship?
The big problem with this is that it gets into fictional cosmology, which never ends well IMO. All of this is pretty vague, so you're not getting much specifics unless I really need to for the story etc.
As some broad points, the Immaterium, being the realm of dreams, is indeed fuelled by emotion and soul stuff
This includes most acts, so hoping fuels Tzeentch, violence fuels Khorne
However, there are other warp entities. For example Khorne has a lot of his violence stuff taken away because of the Orks worshipping Gork and Mork, tyranids or Necrons don't have souls,etc etc. Chaos is merely the largest Immaterial faction, there are others, but the Dark Gods are fish, not the whole pond itself. Big fish though.
We can therefore see that it looks like the Chaos Gods need worship specifically dedicated to them to get the power, rather than just ambient stuff. So maybe ambient violence fuels Khorne a bit, there's always lines about how 'the slaughter of so and so was pleaasing to khorne' etc, but maybe it just means Khorne gets a small bit of power from it, rather than a lot he'd get from actual worship and sacrifice. Also, the Emperor was trying to starve them of worship by being aetheist? That wouldn't have worked if they were fuelled entirely by ambient worship.
Additionally, the Cabal stuff in the Heresy indicates that the Dark Gods couldn't survive in a dead (or at least greatly reduced galaxy):
The end result of Horus' rebellion and conquest of the Imperium would be the total extermination of the human species within two or three generations. However, if humanity were to disappear from the galaxy, the Ruinous Powers of Chaos, whose own existence within the Empyrean depended upon the baser collective psychic emantions of humanity, would be extinguished with it.
This is dumb though because htere would be other species around. The Eldar getting wiped out didn't kill chaos, why would humanity getting wiped out?
Moving on, we also know that alternate worship keeps chaos away. You don't get Chaos Orks (except in weird lore), and even if Khorne was bugging a particular Guardsman, that individual's worship of the Emperor protects them. So whille the Chaos Gods are powerful, the Emperor is more so, or so it would seem. In the recent lore Gulliman is becoming a god because the Imperium is worshipping him etc, and the Emperor seems to be waking up too.
On your point about bloodbanks, technicalities don't work. Or at least it would be stupid if they did. For example, you could more sustainably get blood by requiring everyone on a planet to donate a pint each month or something, or by having an automated skull harvesting something or other. The problem would be that this provides no 'imagination' for the Warp. Similarly, I often wondered if Khorne would get power from robot deaths. If you built robots and sent them at Khorne berserkers, the robots have neither blood nor skulls, so surely they'd provide no 'worship power' in battle? Well, I'd suggest no they probably would, Khorne would be fine with the robot's oil instead of blood etc, because he's a being of imagination not strict rules, and the battle as still honourable etc. 40k's cosmology doesn't work the same way as DnD or similar where there's strict charts or something. You could in theory be a lawful dude and still be a khornate worshiper, as long as you were deidcating your kills to khorne etc.