wow, what a horrible experience!
Good work on keeping your cool throughout (so far) the process.
I almost exclusively buy second hand for frames, shocks, forks (got stung once out of maybe 10forks) and wheels; but obviously new for drive train, brakes, contact points & consumables. Buying ex-demo from bike shops I’ve considered, and once came as close as getting to the till (then card declined for the monster bank shock amount and then never returned).
But somehow not sure, ex hire or ex fleet especially on anything more hardcore than trail centre type bike I would always go new. On XC marathon & road stuff I wouldn’t have any qualm’s, but heavier stuff you just know someone is going to have really made sure they have gotten their 20 quids worth of riding out of it, each time 🙁
Forks *could* be repaired with fresh ano + bushings, but again £200+ easy. When honestly you could get away with just riding them into the ground (1-2years use?) then just get something else down the line.
As for repairs, I guess the only sensible option is go full on, get it back to how it should be, take it on the chin that the used bike + repair will likely cost more than RRP.
And most importantly, once its back, built up and your riding it, FORGET ABOUT THE WHOLE THING, don’t waste any more precious riding time worrying about it, as it’ll only get you down and put a taint on things.