بسم الله الرحمن الرحيم
(Fatwa: 1531/1023/L=12/1434)
You can perform salah behind him. Whatever you mentioned about him is not very clear and it will not invite any kind of harsh ruling against him. However, if there is any other person available who knows the rulings of salah, follows sunnah and avoids sins should be made imam so that there is no deficiency creeps in salah.
Allah knows Best!
Darul Ifta,
Darul Uloom Deoband
