I can't say that I know a lot about healthy, functional relationships, but that sounds like a good foundation for one.
[This should be a little awkward, right? But that future wasn't real and they were just friends with benefits. Pretty great benefits. Felix appreciates physical connections (craves them, almost, after being isolated from the rest of humanity for months on New Caprica), but the kind of emotional intimacy that Jack and Ianto are working on... that's not something he wants now. That kind of intimacy involves a lot more trust and patience than he's prepared to invest in another person.]