(1) Avoid consuming meat at the restaurants of non-Muslims. Yes, if you are sure that the meat presented there is slaughtered as per the Islamic way, then there is no wrong in eating there.
(2) If a person offers salah with jamat, it is acceptable and it will be considered a sign of his being Muslim:
وفی الشامی: الکافر اذا صلی بجماعۃ یحکم باسلامہ عندنا۔
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband