Do you own any polarised sunglasses? All LCD monitors emit polarised light. If you get symptoms when wearing polarised sunglasses, you are going to struggle with potentially all LCDs. I have some sensitivity to polarised light and can't wear polarised sunglasses without eye pain.
If you are ok with polarised light, then your problems with LCDs will be more to do with flickering, dithering or colour spectrum - which generally means your brain and eyes have to work harder.
If your NEC caused you problems then other old CCFLs are unfortunately not likely to be better. But if you can find them cheap second hand its worth a try.
I have another quite abstract suggestion. Depending on what I eat, my monitor induced eye pain can get much worse. I can't eat any cooking oils without problems. If I eat anything with sunflower oil the monitor I am using at the moment becomes unusable. Could be worth eating nothing but bananas, or rice for a few days and seeing if anything improves for you.
No reason you can't use a keyboard and mouse when playing on your plasma. I used to use a piece of wood so I could use keyboard + mouse on a sofa. I think there are actual products you can buy for comfortable sofa keyboard + mouse gaming too.