They way I do it is after adding your LUT to a node just adjust the key output. Anything less than one will reduce it's strength.
If you're looking for the absolute cheapest I would go with the Panasonic G7. It has good tools for filmmaking and is also really cheap.
No. Please don't. Please. If you're going to buy or rent cine glass, might as well make it worth it with a nice camera too.
I would edit in a 1080i 29.97 sequence with an upper field first. This way all your DV footage with stay looking how it is and the 23.98 footage will have a pulldown. If you have 25p footage, that should also work in there.
As far as conceptually, I can't really help you without knowing what the footage is. I just finished a project with both NTSC and 1080 23.98 footage, and for that I used the HD footage to push the narrative with the NTSC intercut to show flashback examples.
That might not be of use to you though because like I said, I don't know what the footage or edit looks like.
Well it really depends on the mood you're trying to convey. I would say the easiest way is to take your light panel and put it in the middle dash. This way it looks like the lights from the radio and such are illuminating their faces. You can also try getting some cheap USB LED lights and set those up in the visors. For power you would use a USB car nub in the DC power outlet. Those are probably the two cheapest ways I can come up with.
To get a ProRes export just go to the quicktime option. The first option is to choose your codec. Your situation probably calls to export a ProRes4444. Set your audio tracks and resolution. Then you should be good to export.