The problem with Jack on DW - and the reason why he'll never be a long-term companion - is that he's simply too knowledgeable and capable a character... and that was before they made him immortal! DW is the Doctor's show and that means that for the Doctor to shine, Jack would always have to be taken out of the equation early on. And so he gets chained up on the Valiant for a year rather than actually doing anything - he really is better off on TW, where at least he's allowed to participate.

But that year in chains does allow for some interesting explorations in fic, so I guess I can't complain too much!

It's hard to tell how much time passes between the victory and Jack's departure. I get the sense that it's probably not very long - he has people he wants to get back to and the Doctor has made it quite clear that he's not comfortable having Jack around (I can only imagine that the TARDIS is even less comfortable with him after he's taken a machine gun to her innards). Plus, I doubt that Jack wants to spend any more time on the Valiant than he absolutely has to!

Which is a long-winded way of saying that, yes, he probably knows Tish a lot better than Martha when he leaves, though I'd imaine that he keeps in touch with both once the Doctor has gone on his way once more.

Glad you enjoyed the fic! :)