Metacam is really hard on the liver or kidneys can't remember which but I think kidneys. When vets first started using it, they were using the same dosage strength used for dogs. Guess what...cats are different and it ended up killing/harming some kitties. The product is black labeled in the US. In Canada, they came up with a reduced dosage strength meant for cats. However it is a pretty hit or miss if a kitty will still react to it. Jones didn't, my civvie ended up with the runs, off her food after her dental. So, for me, all my cats are on the do not use list for metecam.
Covenia - is an inject-able anitbiotic, that if there is an allergic reaction..you can't get the AB out of the system. So it is great you don't have to pill a cat for 10 days...but if something goes wrong you are stuck. I am not sure if there is a lot of cases of allergic reactions..but there is a chance.
I am in Alberta...so everything is higher here...my civvies dental cost 1200 for 3 extractions, xrays, cleaning, in hospital care and the meds to go home with. So I think that is a reasonable quote. Maybe someone from ON can jump in and answer.
Just a note, you can have inflamed gums due to dental disease. Happens in humans as well - that old bleeding gum thing when you brush. Doesn't mean there is an infection per se but the gums are not in good health either. For my civvie...there were 2 teeth that were reabsorbing under the gum line...couldn't see a thing by visual check, but she was in pain and things were inflamed underneath.
I don't think it is pancreatitis as you haven't mentioned some of the common symptoms of it. I really wonder if there is something going on underneath the gum line.
That vet is not good with FD. Let us hope he can do the dental and then you can move on.