Gem freaking out was just bad writing. If Jax had ever thought she had killed Tara it would have been instant confrontation. Able is a really bad child actor.
You know I love kids and it sucks to say that, but he really really is. That being said, I'm sure we're going to find decapitated squirrels or something equally serial killer-esque in Grandma Gem's bed from the future psychopath.
Nero and Wendy end up in Mexico with the kids.