Torn on Dental Work

I have a 20 year old stage 3 cat who is crunching HORRIBLY when he eats. I mean it sounds like he takes breaks to chew rocks as he's eating soft foods. We've tried pate, blending his food into liquid, softened kibble in the hopes he'll swallow it whole, it all bothers him. We have taken him to vet after vet to try to figure this out but aside from some tartar build up, nothing crazy for his age, they couldn't see anything that could cause this until a dedicated small animal dentist noted he seems to be absorbing a tooth. But even then that's a guess at why he's doing this. I know that's very painful and I'm giving him a bit of gabapentin to try to help manage it but slowly increasing it so he doesn't get too loopy hurt himself moving about the house as he's a but frail and unsteady from lack of food. We have floated a dental to try to see if that would help but honestly eveyrone involved is hesitant.

He's so old, he's lost weight to 9lbs when he should be about 12lbs, has a heart murmur, high blood pressure and a fatty non cancerous tumor. My family, my regular vet, and the dentist are all concerned. His pre blood work came back looking alright as it could for the situation, and we would pay extra to have an anesthesiologist remote in for monitoring but still... It would be a risk that I won't have a cat at the end of this.

But on the other hand I don't want him in pain; this is the biggest issue with his quality of life right now, otherwise he seems pretty happy just tottering around the house and getting cuddles. Should I just maybe pursue better pain management options? Everyone seems to be at a loss, as nothing can be guaranteed, we don't even know if after we go through all of this if the dental would even help his crunches.