I'd just pull it up and replace it with good plywood then. That's even easier. No need for perfection with that one. How old is your house?
Not too terribly. It was built in the early 70's but It was unloved for a very long time. I got a very good deal on it but it needs some rehab. For example, underneath the upstairs bath the ceiling shows signs of replacement. So I'm pretty sure it has had water problems before.
So subfloors are just plywood? I remember seeing a "This Old House" where the dudes went through and screwed the floors down after putting some baby powder in the cracks to solve squeaks...at least I think I remember seeing that. They definitely went through and screwed the floor down.
Do you think I can squeak by with a hand-held saw? I probably need to borrow or rent a table saw huh.