A small antenna in an attic is not going to be up to the task. That you see a signal from KUSA is quite remarkable, the conditions shown on your TV Fool report are 'deep fringe'.
For what it's worth, the FCC is on your side. Their OTARD rules supersede the HOA and any zoning rules.
http://www.fcc.gov/guides/over-air-r...n-devices-rule The FCC has put rules in place which protect your right to use an antenna large enough to receive the signals you want.
Having said that, the mountainous terrain around you is quite challenging. I'm not willing to say you have no hope of receiving the UHF signals from Denver, but to have any chance at it, you need to mount outside, in the clear, as high as practical. You'll need to use the largest available UHF antenna, Antennas Direct 91XG or Winegard HD9095P. I can't guaranty success.
The VHF signals are a bit easier, an Antennacraft Y10713 or YA1713 from Winegard would be my choice.
You can combine the UHF and VHF signals with a UVSJ. I would use a separate preamp on each antenna, then combine the signals. The Kitztech KT-200-COAX or Antennas Direct PA-18 would be good options for preamps.