On the Hanson side of things, the simple fact is that in this particular case, it looks as though the situation changes based on your choice to make it the right one. If you side with Hanson, she wasn't infested.
If you side with Selendis, Hanson turns out to be infested herself, and the colony turns out to be a writhing mass of twisting flesh in a matter of minutes.
Now, it has been awhile since I've done the mission and sided with Hanson, but if I recall correctly, she was infested regardless. I could very well be wrong, but I think I remember being shocked the first time when I did side with her, and then discovering it didn't matter and the Protoss were actually right.
In any case, I agree with your Tosh/Nova decision 100%
It's not that I ever thought Tosh was a real "bro" until you helped him, and his motivations seemed outside the scope of helping the cause and humanity, but as you pointed out, he DID offer up jobs, resources, troops, and insights, and after you help him, he offers you friendship as well.
I never picked the Nova option, but I don't feel bad about it. Tosh never seemed like a bad character to me, and though I'll admit I did have to consider it (she made a rather compelling argument, and the fact is we WERE releasing criminals,) I still feel the decision was a good one. When he told me someone was conspiring with Mengsk, I thought, "It could be him throwing me a curve ball, but it could be anyone..." and I started evaluating EVERYONE on the ship because of that.