he clearly had no respect for it, and acted as though he had a right to keep slaves in that state
Washington complied with the law of state of Pennsylvania. What he believed is immaterial. His actions complied with the Law in the State of Pennsylvania.
Skirting the edge of it. He probably didn't want to blow up the fragile coalition by defying it outright.
He went to so much work to put it together that he was loath to strain it.