TBH I don't think Magick Archer is as fun as some other classes, although it dominates in Bitterblack Isle. I used others for the main game, and then switch to MA in the post-game/BBI.
As to pawns, when you hire someone else's pawn it's frozen in time effectively. It won't level up, and the way it changes in the pawn owner's game doesn't get automatically reflected in yours. When you finally release that pawn, the rating, rift crystals, gifts, and items you equipped on the pawn, and any new item/quest knowledge, get cached, and the owner will get them all the next time they rest at an inn (which is also when any changes to their pawn get updated for the game's hiring system). If you then go to hire that same pawn again from a riftstone, you'll see the most recent version of their pawn.
Only you can level up your main pawn, and obviously the same goes for other players. So the game is built around encouraging people to regularly swap out their hired pawns.
On the bright side, if you were using underlevelled pawns then you would've been getting more xp than you would've otherwise
Most of your gear upgrades will come from buying stuff, and then enhancing your gear at vendors using materials. A big part of the game (for me anyway) is finding what materials are required, and then hunting them down in the world. You do get the best stuff via equipment drops, but they're generally tied to big events (i.e. powerful enemies, quests, important locations) rather than being stuff you get from random encounters.
This is very true, and the Souls games are the same. They very much let you off the leash and expect you to learn from your mistakes. It's both a blessing and a curse.
BTW, before completing that quest you're talking about, consider heading back to Cassardis for a quick visit.
There's fast travel, and your stamina obviously increases in line with your character during the game. That said, the game is very much about exploration, planning your routes, trying to make it back to cities/safe places before darkness falls. The fast travel system in DD is designed around that.