Squirrel has rabies or lead poisoning?

lead poisoning, like most heavy metal poisoning, typically doesn't manifest that way. (heavy metals usually kill secondary to renal or hepatic failure as the technical cause of death.) Rather, this would tend to be indicative of rabies virus, unless there is some other unknown poison in the area. The things to look for would be boron-based pesticides as well as warfin-based pesticides.

The squirrel may have an inner ear issue in progresses

Squirrels almost never ever have rabies, not sure about lead poisoning symptoms in animals even if there was lead in the paint. You can ask the health dept

Rabid animals don't really end up with "foam" in their mouth. They hyper salivate... aka excessive drooling. either way best to leave it there and call animal control. If it bites you and it does have rabies, you're in serious trouble. Rabies is 100% fatal if you don't get the shots right away.