Hi, there's a "Report a bug" link up at the top of the game launcher that will send you to the right place in Larian's support site to officially report bugs.
People are very welcome to report here, too, but that's more to check whether other people are having the same issue or if there's a workaround.
On which note, could I just check for item (2) on your list, which entrance are you trying? If it's the one down the ladder then it's only a small hole and you won't be able to get in unless you yourself are small. Were you already aware of that? If not and if you can't make yourself or one of your party small, then you might need to wait for another opportunity to get access via another entrance ...
Doni can be persuaded to show you the entrance after he disappears and reappears, or if you save Mirkon on the beach he'll give you a pass
That all said, I also had what seemed to be a bug with the recover belongings quest, in that I couldn't ask Mol to give my stuff back as I could in early access. Unless there's now a different way of getting it back that I didn't spot.
