SK, long time no hear, so welcome back. I'll just touch lightly on your question (1). The difficulty in judging HDMI suitability arises because three factors are involved: the strength of the output from the sending component, the loss in the cable, and the sensitivity in the receiving component. Because of variations in the other two factors it's possible that a certain gauge cable will work perfectly at a certain distance in some setups, but might show some sparkles in the picture in others. In general, it can be said that for a run of around 30 feet the 24 gauge cable should be selected rather than the 28 gauge which is fine up to maybe 20 feet. If you haven't read it, Blue Jeans Cable has an excellent discussion on this in their
Tartan Cable section .
In any case there doesn't appear to be any good reason to pay more than about $30 for a 30 foot 24 gauge cable either from Blue Jeans Tartan or similar from MonoPrice. There's no mysterious "quality" factor unrelated to signal strength loss which justifies spending maybe ten times as much.
If the HDMI is to be run in-wall MonoPrice makes the useful suggestion that the cable be tried first before being installed in the wall to assure that it's suitable for the conditions.
