Nah man, Tom knew about Pentangeli's survival from Fredo, he relayed this news to Mike. Fredo probably told Tom about Questadt too but Tom let Fredo hang on to that and tell it to Mike himself, as it may have gotten him off the hook.

Tom's coldness to Fredo at the wake is explained simply because Al was watching them and Tom knows that if he's nice to Fredo, Al will go straight to Mike.