I've had two close people get fusions. One was after a year and a half of severe pain, arm numbness, corticosteroid shots (useless for him) and painkillers, and completely sedentary behavior that had his health go to shit. The fusion completely cured him, slight loss of ROM only. The other had many months of degeneration and unfortunately putting off the surgery (insurance fuckers, mostly) led to one of the two shredding discs impinging into some critical ligaments and the surgery wound up much more extensive and traumatic than planned. The double fusion took nicely and is solid but the surrounding complications are still a huge problem causing nerve impingement and muscle spasms requiring tons of drugs, and further surgery seems likely to me. Dunno if another disc is going but more scans are needed. Scans are limited in what they show though, not the all-seeing miracle tech some people think. Surgery winds up being the best way to finally see what the real situation is unfortunately.
Discs never heal do they? I'm not aware that any of these other treatments can do anything more than mask symptoms for a while. I'd go for surgery before the discs start permanently fucking up surrounding tissues.