If you can get reliable reception of all the signals you desire with an attic mounted antenna, great, the antenna will last indefinitely, protected from the weather. However, attics can cause reception trouble, particularly if there's metal close to the antenna. If you try the installation in the attic and find unacceptable performance, the FCC protects your right to install outdoors, over-riding HOA rules.
http://www.fcc.gov/guides/over-air-r...n-devices-rule
The ANT-751R is a very good fit in your case. I would avoid the TVPRAMP1R. If an amplifier proves necessary, the booster in the attic may be appropriate... what is the make and model of the booster?
Do all cables from the TVs run into the cable box? Or, does one coax come out of the box to a splitter?
The rest of your concerns are important but let's work on understanding your existing cabling arrangement so we can keep you from mixing cable company signal (phone/internet) with OTA. Then the answers to the rest of your questions will come in to focus.