I'm also a big fan of having a 6 month emergency fund, in CASH. I'm OK if it isn't earning anything, because it is money I dont want risk associated with. I suppose there is inflation risk, but that is why I have a little(and I do mean little) saved in gold, just for that off chance that inflation gets crazy.
OR would this extra money be better spent going in to the Roth to max out 2015 and 2016 right away? Knowing if we did have an emergency I could in theory take it out again?
Issue I see here is the early withdraw penalty, and it could actually loose value between now and when you need it, leaving you with less than 6 months savings.
should I put some in I bonds every month to start seasoning another $7000 in emergency fund?
This is an idea I have considered as well, but in addition to my emergency fund, and more like a low interest savings account that cannot be touched for a while. But you may not be able to access it when you need it.
OR would this extra money be better spent paying down the car or student loan? Both of which are not high interest debt.
If I were in your shoes, I would get serious about knocking out both and quick, instead of investing. The interest isnt to bad, but the car is a depreciating liability, and the student loan will NEVER go away, even in bankruptcy, unless paid off. When those payments are gone, you now have $400+ per month you can stash away! And never have to worry about paying on if you loose your job before FIRE, and makes obtaining FIRE $400 less per month.
Just my two cents.