The Tavern

If I leave a treasure trove, will I be able to get back in there? Or are they like timed portals in this respect?

You cannot go back.

If you get banished from a Trove, will you return inside it from the Abyss?

Please do us all a favour and try it out, wielding/unwielding a distortion weapon. And then report the result here...

Yes, you will return to the trove if you escape the abyss.

If your character is strong enough, you can use this technique to scum Abyss for gold for a Bazaar.