OK, to answer your questions:
2) color - OHP can print any dang color. I'm assuming the lighter the screen color, the closer the text color will be to the natural greenish color of the VFD. (Remember I'm trying to match the red instrumentation of my dash.)

In a manner of speaking, yes you are correct, the lighter the colour the less influence it will have on the colour of the VFD. However it will also depend on the saturation of the colour as well. I take two print passes with the colour as I find it helps to get nice rich colours. If you want something more subtle then one pass will probably be sufficient. You should have no problem achieving the correct colour to match your dash lighting. You might have to go through a bit of trial & error to get it just right though.

3) Glare - Based mainly on how shiny or matte the top surface of the screen. Some have suggested using 600 grit sandpaper, sandblasting, or some AR coating.

At the moment mine's glossy. I've had a quick look around the web for some aerosol anti-reflective spray and all I could find was this. Unfortunately they don't have an agent here in the UK at the moment but they are working on getting it manufactured here. I haven't tried ordering any so I don't know whether they'd ship it over to me. I've thought about bead blasting (a bit kinder than grit or sandblasting) but haven't actually tried it so I don't really know how it would work out. I think it might make it too matte so you might have to do some gentle polishing to give it a kind of silk finish. I also thought about the possibility of using some of that spray on Glass frosting or some silk finish lacquer.

4) VFD reflection - direct sunlight being reflected by the unlit portions of the VFD display. Problem mainly experienced in sunny California; not ready to move to the UK (althought the customer service is better there, I hear). arrreerrrr, different thread....

I do find that in brightish sunlight it is difficult to read and it seems very dependant on the screen colour. As you've probably seen I have a multicoloured one at the moment and it really depends on how the sunlight hits the screen as to whether it's the darker or the lighter colours that get washed out first. YMMV of course.

Beaker, how do you attach you OHP film? Do you use a clear plastic lens? Does it have a matte finish? Do you mount it outside of inside of the lens? Does Macromedia Freehand work with your Corel 5.0 files?

I mount it instead of the lens. I don't have a colourless one that I can use although I do intend making one and doing some experimentation with blasting etc. I've no idea whether Macromedia Freehand will read the CorelDraw file. Sorry.

Basically just experiment. That's what I did and the results have always been more or less satisfactory. My method(s) are not definitive and I don't pretend that they're as perfect as a professionally manufactured screen but they are more than acceptable (IMHO) and offer the opportunity to get colours that aren't available elsewhere.

I hope you have a go and you are as pleased with the results you achieve as I have been with mine.