T-Mobile has a home internet service at $50/month or so that might serve your main purpose. However, I'm fairly sure you can't take the included modem/router traveling (someone correct me if I'm wrong).
Anyway, my main concern is that hotspot data might end up being significantly more than paying Comcast for a basic plan, even if you don't stream or download much. Something that may be worth looking into is signing up for Google Fi and getting an extra data-only SIM card for your home connection. It's $20/month + $10/GB for one voice line but after something like 6GB they don't charge anything extra. You are subject to throttling after something like 15GB or so, though it sounds like you might not hit that--and if you do, it sounds like you can bypass throttling by paying $10/GB for data above that level.
As for devices, I personally use
for traveling and it works reasonably well. It also supports a sort of "bridge" mode using USB, which in theory should be usable by a router running OpenWRT or similar. I also have the external antenna for it but I've never needed to use it, so YMMV on that.