The furnace kicking on thing could have just been a coincidence that happened a few times.
Used a wired PC last night for an hour or so and had no issues. Will do that again, maybe trying to use both it and my laptop simultaneously to see if the laptop drops while the pc continues to work. I thought I had pretty much done this testing, but now I'm starting to doubt myself. Maybe the internet started working again in the time it took me to set down the laptop and walk over to the PC?

If the wired computer never drops, then the problem isn't comcast.
This is driving me crazy....and the fact that I'm letting a 30 second inconvenience every hour or so drive me crazy is driving me crazy.
I'm starting to think maybe it's my laptop. I had ruled this out because the nexus player which also relies on wifi had reported it was connected to the network, but not the internet several times in one day. Same as the laptop was doing. The nexus player hasn't had any issues since though. The firetv sticks haven't seemed to have any issues.
Maybe this points to interference. Maybe the laptop is using 2.4Ghz while the firetv sticks are using 5Ghz. The only other 2.4Ghz devices in the house are wireless keyboards and mice which I unplugged. The router is less than 20ft from my laptop and the neighbors houses are at least 50ft away on two sides and several hundred feet away on the others.
Maybe it's aliens.....
Came across a used wifi card for my laptop on ebay for $4 shipped (from the US), so gonna give that a try for lack of other ideas.
I already have any power saving features that would disable wifi turned off btw.
Also moved the wifi channel to the emptiest spot (channel 9 with no neighbors on 8 or 10 either).
Not sure how to go about testing for interference, especially if it's in short bursts.
Maybe the software defined radio program I have goes that high and has a recording feature....