Yes, I have read that too, I just thought it was normally more rapid than what you are experiencing - but I have no idea really.This is what I have on Marek's
What I don't understand is how he could have gotten it if every chick was either vaccinated or hatched here? I haven't introduced adult /older chickens to my flock, only vaccinated chicks. So, where did it come from?
I don't think it will help you decide what to do with your poor roo, but there is a PCR test for Marek's. It might help you with future flock management to know if you really have Marek's in the flock or not.
You can get it done at a private lab in Texas (if you are interested I can find the link) and for all I know the State vet would do it too.