Thanks very much for the compliments about our forum and welcome aboard. You'll get plenty of assistance here.
I agree that reading NFPA70 is like reading the Bible in reverse. Fortunately, your situation is not subject to a lot of scrutiny as long as you do a clean job and don't act like a fool.
Let's get the legal stuff out of the way first. Any type of cable that is rated CMX is limited in length to 50 feet and only for use in residences. Will this be caught by an inspector? I doubt it, but I'd think that you can get RG6 with a CMR rating for the same price. Buy quad-shield RG6 if it doesn't break the bank
White PVC pipe is technically only approved for DWV (Drain/Waste/Vent) applications when used indoors. Any connecting conduits for your wiring should be contained within gray PVC electrical conduit. Schedule 40 is the standard and will be fine for your application. I really doubt that you would encounter any resistance for using either type for just a simple wiring chase.
Vertical penetrations between floors or even through a sole/top plate require fire stopping in most places. Usually, this is done by using red caulk. Because of this, I prefer to spend an extra two bucks per outlet and use a piece of 3/4" ENT ("Smurf tube"). Fire stop that thing all day long, yet you will still have a clear channel to add/remove wires from above or below. ENT is sold in 10' lengths at most home centers, so leave the excess in the attic, especially for outlets on outside walls. That way you won't have to crawl so far into the corners of the attic to get to the end. You (or a future installer) will appreciate that extra three feet sticking up through the insulation.
Always, always run an empty conduit between floors as you have planned. 3" might be overkill, but why not? An inspector will likely insist that you seal both ends with fire stopping caulk to prevent drafts. In my area, all that is expected is typical foam spray to block vertical draft.
CAT6 is overkill, but if that floats your boat and you have deep pockets, then go for it. You are only adding expense and labor for yourself by using it. If you follow the concept of using tubing/conduit to open all possible pathways in the walls, then you can rest at ease. You can pull next year's technology in with a simple trip into the attic.
My personal attitude about wiring houses for voice/data/video is to pipe them, not to wire them. Throw in some empties on as many walls as you deem practical. The extra few bucks might make you day when it comes time to move furniture.
