To address how well Tristan can play with others: First, I know that the game is currently in the wake of some divisive inter-party conflict and that you're just making sure the game doesn't return to that, but let me reassure you right off the bat that I wouldn't make a character who couldn't adventure with the other player characters. It's not the TillForPie RPG, it's the Dungeon World: From The Outside RPG, and we're all responsible for ensuring each other's enjoyment.
For instance, note one of the bonds I listed for Tristan: "I respect the beliefs of Hawthorne but hope she will someday see the true way." So while it's clear that he feels his way is the correct one, he's not incapable of acknowledging the righteous members of heathen religions (and I use "righteous" very purposefully here because note, also, that his "quest" demands he protect the defenseless righteous without making mention of faith or race). This all ties into why I have no interest in playing a young Tristan.
As for his alignment, I picked lawful for him rather than good because, well, he's not good. He's the epitome of how life has a way of wearing away who a person is day by day - and he's seen a lot of days. Toiling for decades out of obligation to an ungrateful god is what he's all about, and that makes him lawful in this player's humble opinion.
So in short, no need to threaten me with a smack-down. I think he'd get along with the group, and if there comes a time when he can't he'll either change as a character or be retired from play. If the above sounds unreasonable to you I wouldn't mind coming up with another concept: I'd rather come up with another concept that excites me that you think would work than water down one that wouldn't.
As for the quest, all that particularly matters to me are the two boons but if a questing isn't something that Tristan would be constantly doing it'll mean he couldn't have been trapped for months as suggested but that isn't too important.