A neighborhood lawyer. Don’t need anyone fancy for this; just the local dude with a general practice. Even better if his specialty is real estate closings, cause then he’ll be familiar with title searches etc. I’ll be surprised if this costs more than a couple-few hundred buck.
He would want to first see if there is an easement recorded in the deeds. If there is, then you’re done. Even if there isn’t, the right might be created by the long term usage you both have done.
Personally, I find it highly unlikely that the houses and driveway would be built in such a way if there wasn’t an easement.
Then, during the trial, tell him he can’t handle the truth.