Finished all the main quests, but don't want to move on until I've hired Tomi to open all those chests and doors I previously couldn't get into and scour the areas LOL. Well there is this one door in the Blacklake District, right above Hodge's house. I can't get in there! Even Tomi couldn't. I'm thinking this may involve artifacts, but already put the arrow and/or the sword in the crate next to the door, but no go. What am I missing here? I want in there dangit!

That's part of the mage only quest. There are wizard labs in each district, each part of a Cloaktower quest. If you're not a wizard, sorceror or bard, there is no way to do the quest. You're not missing anything. There's no treasure in there, just a magical component.

on that note, is the zoo some sort of Druid/Ranger quest? I couldn't figure out what to do in there as a Fighter/Rogue

you can do the quest with any class, my dwarf fighter completed it a few days ago

For the zoo quest, go to the tree grove right by the Halls of Justice in the City Core. There's a druid there who will ask you to free the animals, and give you a scroll to use on the tree within the zoo. You'll need to persuade the druid if you're not a druid or ranger, but you should be able to do the quest.