The expressions I don't understand
This is the part of the lines of TV series "Friends"
1)
Listen er..I need to ask you a favor but you can't tell Monica anything about it.
Joey: I thought you didn't have secrets from Monica.
Chandler: And that would have made the official party line. (Joey nods) Monica and I are having a little financial trouble.
What does "would have made the official party line" mean?
2)
Mike: Well hey, I wanna ask you about Monica's little "groomy" joke.
Phoebe: Oh! Alright. Well I think the reason people laugh is because it's a play on the word roomy.
Mike: I get the joke. Sophisticated as it was. Now the thing I wanna say is... maybe we should have talked about this before. Us living together, you're not expecting a proposal, right?
Phoebe: Oh no! No no! Not at all. We're just moving in right now. See where it goes.
Mike: Yeah well, that's the thing. For me it's as far as it can ever go.
What do "Sophisticated as it was" and "It's as far as it can ever go" mean?