Looking for recommendations crossing Idaho

I'm currently following the bike nonstop route from Portland to DC. I got a late start.

I'll reach Ontario, Oregon in a couple days and am looking for a possible alternative to my current route. I am desperately trying to get over the Rockies as quickly as possible. I've literally contemplated just interstating it, although not ideal it looks like it'd save me a ton of elevation and maybe distance.

Current route is taking me through Boise National Forest up to Challis, down to Rexburg and then crossing into WY. Does anyone have insight or advice?

Thanks in advance.