Why does jack remember? Well.. that's all the more difficult to understand I suppose.. I always assumed its due to how his brain is wired from his Debilitating mental illness. But otherwise? I'm not so sure.
As for Jerry, well.. if you had taken a bunch of Drugs, having tazered yourself for fun, and joined/survived a murder cult that wanted to blow up the world, you'd also might just be as invincible.
However I do enjoy your speculation! It's always fun to see someone think outside of the box.
-You already Know