First off, you have added to a thread that was started 14 years ago. It's better to start a new thread with your questions when the other ones get to be that old. You're forgiven though, because you just joined....
To answer your questions:
1) The paper-covered wire bow does attach to the roof support with "teeth" that stick out from the support. Not sure on a '64 sedan, but the dome light should be behind the roof support, and those teeth are in front of it. You start hanging the headliner by hooking the wire bow over those teeth through small slits in the bow sock, then bending them up carefully with a hammer so the bow can't come loose. The other steel bows should have been numbered when removed from the old headliner, but it sounds like they weren't. Maybe someone else will know in which order the paint markings refer to. Each bow should be a slightly different length and curvature. Generally, the shorter straighter bows go to the front and then they get longer and more curved as they go rearward to match the curve of the roof. You should be able to match them to their corresponding holes in the side of the roof by trial and error before you install them into the new headliner. Then number them with masking tape.
2) Correct, no longitudinal support except the bow that hooks onto the teeth.
3) Again, not sure on your car, but many GM mid-60s cars have a tack strip that is stapled or screwed to the roof behind the windshield. You may have to install new tack strip so you can staple the new headliner to it.
4) The rear window should be similar to the front with the tack strip ahead of the window.
5) Most GM cars up to the mid 60's just used tension to hold the headliner bows in place. Later 60's cars had a plastic clip in the center of each bow to hold it up there.
Other members on TC should be able to get more specific on your '64. My answers are from general experience with 50's and 60's GM cars.