@dtherio I feel your pain as I have lived through exactly the same.
Between my antenna, spliter, Tablo, hard drive, android Tablet and misc I was into this cord cutting adventure for around $800 myself only to find out that Chromecast wouldn't work. By the time I came to this realization it was past my 30 day window to return to Amazon as well. I admit mostly cause I was traveling for business but again my issues where never resolved by support and they quite responding to my ticket and emails.
Luckily for me I'm some what tech savvy and by the grace of your favorite deity I was able to use @cjcox python script to integrate the Tablo into my Plex media server. If it wasn't for that I'd up the proverbial creek without a paddle.