Without seeing him, I don't know. If you are able to post a video of what happens when he moves or tries to stand it might help getting suggestions. And pictures of his eyes that you say are pale. I'm not an expert on Marek's, but if it's paralysis then it's certainly possible, and there are others here who have more experience with Marek's. If you are able to do video you can post on youtube or other host and link to it here. Is he eating and drinking normally, is crop functioning normally (full after eating/empty first thing in the morning) , and what do his droppings look like? What do you feed, including treats?
Edit: if you can tell where you are located generally, it may help also.