I totally agree that some vets put way too much pressure on owners to spay/neuter. It is a very personal decision and nobody should make it for you. If you have a problem surgically removing organs because your dog "might" get cancer someday or an infection, then skip the surgery.
On the other hand, I had no idea that there were health benefits to spaying when Ellie was a pup. Nobody told me. While I think it is very unnatural to be removing organs and I hate the thought of it, I also think that a 26% chance of getting mammary cancer is just too high and the chances of pyometra (requiring an emergency spay) is very high also. After talking to Ellie's vet, I went ahead and agreed to spaying. Ellie's heat cycles were irregular, so we already had a clue that a hormonal issue was occurring or could easily occur. She had too many heats for spaying to protect her from mammary cancer but what the vet didn't want to see happen was for Ellie to get pyometra. Then, while her body is trying to fight a serious infection, she would have to have major surgery. It is hard to get a pus-filled uterus out of a small dog without spilling it and it was much safer for Ellie to undergo the surgery while she was as healthy as possible. She did just fine.
I have heard of no good reason why tooth work and abdominal surgery can't be done at the same time. I mean, when dogs come home after surgery, what do they do? They lay on the floor, incision and all, that is full of germs from shoes. Their abdomen could be draped off before tooth work is done. I don't see an issue but maybe I'm missing something. Many dogs get baby teeth pulled everyday while they are being spayed/neutered.
I know it is scary and I refuse to call it a perfectly safe surgery because there are obvious risks. It should be a personal decision backed on research and what you're comfortable with.