Well, sounds like DL is your best choice, AF and SQ are both partners in DL's program ...

I'd pretty much abandon your UA account and stick with LH since they're both in Star, but unfortunately I don't think either AF or SQ are partners with LH (though SQ is a partner with UA).

Regardless, put your miles in DL and you'll have enough for a free ticket when you're done (though if your traveling in coach on SQ you'll only earn 70% of actual mileage I think, and make sure your fair is even eligible for mileage!).