I just figured out the tribes trust problem. I have to say, it's a bit counter-intuitive.
When the garrison gets attacked, and the game offers to let you you add extra garrison troops,
it says you'll lose trust with the tribes, and it tells you your current trust score.
I kept thinking, "well I want to increase their trust, so I better not do that!"
That is exactly what you need to do, add the extra garrison troops,
because that creates an opportunity to regain trust with the tribes.
Barrack, you want the troops morale to be low (not sure exactly how low), then try to enter the barracks area while wearing the disguise used to enter the slums. The guard will stop you and turn you back. Immediately keep doing it a couple more times and his dialogue will progress.
Bar, talk to the bartender, then the purple dude in the corner, then the big table in the middle with four guys. Take their bet and lose the card game. You'll need to come back to them a time or two I believe, and I imagine you'll need your lewdness/indecency (whatever it's called) to be high enough.