When I mentioned data grade, I meant anything that was above video-only (480i). The 9PG+ falls well into that category and can do 720p and up no problem (up to 1600x1200p I think), so you're more than fine. Frankly, it will blow the crap out of my projector.
You're right, as far as I know, CRT is as good as you can get for reproducing what you see on your monitor on the big screen. Don't bother with RTPV's unless you need to have the lights on and want everything in a one-box setup. To get anything even near the quality of the 9PG, you're going to have to go MEGA high-end in a RPTV. Just remember that you're likely going to want to ceiling-mount the PJ since it always tends to be placed right where you want to sit. That's just life with the CRT's.
72" diagonally is just about right image size for most CRT's. You'll have to experiment. I'm sure you'll be very satisfied with the quality at that size, maybe even bigger.
Most people (though definitely not all) on the CRT forum consider gaming to be a poor use of the CRT. Personally, I can see no better a use for it. They tend to say "Don't waste such a good projector on games!". Pretty sad, really. They think we all still play Dig-Dug.
I can't really do much more to push you over the fence. Here is a link to some screenshots of my projector in action. Keep in mind that the camera wasn't steady and I didn't know what I was doing with my CRT at the time. My PJ is 5 times sharper now and yours would be 10 times sharper than that. Mine is video-only with plastic lenses = big, blurry scan lines.
If you need more info, don't be shy.