Is the 4x5 plate the final product or is it intermediary? As in, do you want to enlarge or contact print the glass plate?
Taking pictures of the tv is fine. You want to make sure there are no other lights on. The screen pixelization is less significant the more of the screen you get the image on - and the higher the resolution of the screen itself. I have photographed onto 35mm film a digital photo displayed on a 4k laptop monitor - the pixels (which you can see in the grain focuser when the film is in the enlarger) are not visible to my eyes in an 11x14 print. You would definitely not see them in a contact-printed 4x5.