Today I set out on a long ride (Trenton, NJ to Boston, MA). Before leaving, of course, I had to do at least *something* wrong 

I negligently poured way, way too much oil in. After about 20 miles the engine started to slow to a crawl and began badly smoking everywhere. I was able to do 70, then 50, then 15 mph, and then pretty much nothing. The smoke stopped after the engine was turned off.

If anyone has some advice on what I can do it would be really helpful.

drain the oil out and replace with correct amount of fresh oil. you should also check to see if a lot of oil drained into your airbox through the top breather tubes.
the smoke is probably from oil filling into the cylinders through the valves from the top a bit.