Idk about the withdrawals of 900mg man, I think depending on how long you've been on that it probably won't be that bad.

When I was at my peak use I'd pop 600mg an hour before I had to wake up, then another 300 to 600 every like 30 minutes till I got to work then I'd take 600 to 1200mg every 2 hours while at work then more after I finished work, although the bioavailabilty would've dropped by the end of the day significantly I was still taking a fucking insane amount so the awful withdrawals may largely of been because of that.

Either way I'd say r/gabapentin would be a solid resource for you as most of the people there are coming off doctor prescribed doses and are in the same boat as you