Haven't had Snapdragons for all that long myself, but the flowers don't tend to last long for me, maybe a few days at most. I just deadhead and within a week or two, new buds pop up.

Deadheading is a good idea. That may be all they need. They may be stressed from having their roots mutilated, but it's impossible to divide small pots without doing that.

I've had some for several months (mild winter where I am) and every now and then I deadhead and they come right back out. One that I didn't deadhead made seeds and now I have some volunteers that are small, but blooming. Big surprise when I figured out what those little plants were! I've never grown them before but will from now on.

Yes, snaps stop blooming for a little while when moved. Once established, it should bloom in spurts until it gets frigid. The fact that the foliage looks good is, well, good. As soon as they get their roots back like-they-like-it, the flowers should show up again.