I fixed the lag (so far) by doing that database rebuilding thing proposed somewhere here. But now I've encountered a new issue.
As I enter fort amol and defeat the 3 mages inside, they have loot, but all chests, barrels, drawers etc. have no loot, I found 1 ingredient on top of the closet, drawers contain only tankers and boots, hat etc. but no real stuff. no gold, no weapons, armor, books, potions, etc. Only useless stuff. I checked the UESPWiki for info about the dungeon and this confirms that it isn't "forgotten" by the developers, so it's not generated or something.
Anyone else had an issue like this?

I'll continue anyway and check wether the next random location turns up with loot or not.

Also, most double edged birthdaypresent ever ...

Checked somewhere else, and I found loot.