Focusing on the stations that broadcast from Queen Anne and Capitol Hill in Seattle, You'll be facing significant challenges due to the rapidly rising terrain as you look south and south west. Clicking on the KING-DT link in you TVFool Report
http://www.tvfool.com/?option=com_wr...ALLTV%26n%3d12 illustrates the problem... The graphic shows the transmitter on the left and your receive location on the right. You appear to be in a deep signal shadow shown as dark blue near the receiving site.
Reception in the Seattle-TacomaEverrett market generally calls for an antenna or combination of antennas that cover real channels 7 through 51 though the pending repack will reduce that to 7 through 36. A few areas may see a signal on real channel 6 which I have yet to see it myself (It may or may not be on the air, not uncommon for a lower power station).
In your case, it sounds like you already own the HD Homerun tuner so you have most of what you need to experiment. Two or three stations KZJO, KIRO and KWPX would likely be the easiest to see from the third floor. The first two have translators, one to the east and the other to the NE of your location. KWPX from Tiger Mt. should be line-of-sight from a third story location. Everything else will be a 'try it and see'.
The size antenna(s) that would give you the best chance of receiving from the Seattle locations are likely too large for an indoor install (unless you and everyone else in the home love antennas). I use a roof mounted Antennas Direct DB8e and the now discontinued Antennacraft Y10713 (I'm south of you and atop a hill with most signal 'line-of-sight' but obstructed by 100+ foot evergreens. I could do alright with a smaller antenna but don't consider what I have as overkill.)