first question.. yes. Injecting meth into E85 isn't going to be beneficial. Both are alcohols. Methanol has more potential, but not enough to warrant a meth injection into E85.
You need to have a tune no matter how little or how much E85. I'd recommend to NEVER blend any fuels. Only E85 for your tune, or only gasoline. Study E85 up a bit, and you'll understand why. I personally am about to get an E85 tune, but I will have both an E85 and a gasoline tune. That way I can switch when I switch fuels.