Thanks for all of the comments and advice. I'm hoping to retest in a week or two. I've got a road or two in mind that might work for the 20 minute part. I've heard of people doing a test on rollers instead of a trainer for indoors, but I can see myself falling off of them during the high intensity intervals.
I'll definitely take it a little easier at the beginning of the 20 minute effort. I ramped it up to where I wanted my average power to be pretty quickly and struggled to hold it. After I recovered a bit and realized I was slowing down I was able to increase my wattage back to just under where I wanted for the last 10 minutes. It still hurt like hell, but I finished 'strong'.
The 65 miles I rode the day after was a bit tough, seemed like it took forever to get the legs to warm up. TSS 225. Normalized power 164W.