It took me months to get my OTA setup working. I'd get frustrated and abandon it and then go back later. There's a lot of variables that can affect your reception.
Height of your antenna
Leaves on the trees - Here in North Carolina fall is upon us so I get lots of fringe stations that I don't get in summer.
House construction - metal roofing, aluminum radiant barrier in the attic, wire lath stucco exterior walls - any of these will block the signal
Neighborhood interference - neighbors houses etc.
My problem turned out to be that one of my stations was so close that the signal was too strong and was overwhelming my tuner. I finally solved this with a tiny homemade antenna which is just an 18" length of 10ga copper wire mounted on a scrap of 2x4. Some of the antennas that you can buy now are only UHF. Which in my case is fine as we don't have any vhf stations left. You may need a combo antenna to be able to receive your NBC affiliate which apparently broadcasts on physical channel 11.
Have you tried attaching the antenna directly to your tv? Tv's typically have better tuners than any of the computer solutions. This would at least eliminate all of the variables associated with the pc. I personally use hdhomerun tuners which are located up in the attic with my antennas. This way I don't need any amplifiers etc because of long cable runs and splitters.
Also, and don't take this the wrong way, but what you are reporting about the file sizes and 480i vs 720p etc just isn't possible. These are digital signals. If a channel is broadcasting in 720p or 1080i or even 480p that's what you will be recording. It's pretty much all or nothing. A weak signal won't cause a lower resolution to be saved. A weak signal will cause droppouts and occasionally a recording to fail and stop part way through.My local stations typically broadcast the main station at 720p or 1080i and all the sub channels at 480i. I think this must be what you are seeing. All of my 1080i recordings are more than 5gb per hour.
However, this is something that is worthwhile once you can get it working. I get great reception now with a noticeably better picture than our local time warner cable feed.
Server: Windows 10 - ASrock N3150DC -ITX Fanless Celeron
Clients: Shield TV with X-newa on Kodi, Asus chromebox - openelec - X-newa on Kodi