I liked the way they switched up the teams, too. I was annoyed at Anna at the beginning, because she wasn't very sympathetic about people not wanting to switch teams. I agree that it was the contestants doing the work to lose the weight, and they should be able to work with any trainer. But many of them were just starting to learn to open up with someone, and now to have to switch to a different person that they don't know can be jarring.
I liked the challenge, but I wonder why blue chose immunity for 1? I think they saw the word immunity and just picked it, without realizing that the 3 lb advantage was a much better prize, because it applied to all of them. And I think that's why John felt the need to carry the team, because he knew he had immunity anyway and didn't want the team to think he was slacking because of it.
Personally, I don't think Ramon will do something to leave, because this is a once in a lifetime opportunity, and he and Jessica can wait a few months to start the rest of their lives. iirc, they're not from the same place, anyway, so they'd have to be apart for a while no matter what. If I was Jessica, I'd want him to stay as long as possible, to learn as much as he could and be a help for both of them.