Yeah i agree, especially the scene where Tony thinks hes messed it up and got it wrong i.e who was the rat, thinking Paulie might have already silenced Big Pussy.

But Pussy and Jimmy were both rats for sure. Its been a while since ive watched so my mind is fuzzy with the timeline, but is there any inclination of Jimmy being a rat before there pinched in the social club with the snooker table of guns ?

If not that was probably when they flipped him. I can't remember if him pressing Junior for information was before or after that. I think it was after though and by then they knew to feed him nothing.