Nice to hear you go a refund!
I don't mind 320x240. I play some old 320x200 games even today. And It is enough for some basic console output.
I am pretty sure 640x480 on composite would look really bad if you actually use the resolution. At least with PAL.
(Because of the 4.33MHz pal color carrier. Maybe you have seen TV shows from the 70s where the checked patterns on the coats caused really bad interferences with the carrier and colors went crazy)
That sounds really great!
I am not afraid of modifying a device, but it is nice if you can actually get away with only using the 5V rail. (I had a display once requiring a lot of supply voltages - including something odd like -11V. That was a pain.
I am kind of in a hurry now because I will go on vacation tomorrow for one week.
So if I don't write it is because of that, I did not lose interest in the topic.
Good luck with the display!