Hmmm. Mrs Figg lived "two streets away" but we weren't told her address.
I think there's insufficient evidence for your surmises.

Mind you, it may not even matter who lives at #11 if they end up taking baby Harry to the police and Harry ends up in an orphanage and then gets adopted by someone else. A bit of plastic surgery and a new name, and nobody will know that he's Harry Potter. He'd be treated like a Muggleborn. Whether or not the staff of Hogwarts would notice his resemblance to James Potter might depend on whether they were looking for it...

Interesting thoughts, anyway.