The vaccinating question is a tough one. The strain of MD I had was horribly virulent. I had all three forms in my flock and at least once a week, sometimes twice for almost a year I was culling or finding birds dead in my coop.I haven't had a single one of my birds vaccinated against Marek's and there's a reason for it. I have read white papers and research papers on it, and just like COV, you get vaccinated and it does initiate a response to the mildest form of Marek's but does nothing to prevent immunization against the more virulent strains of the disease. I also don't have Gator vaccinated against kennel cough yearly since it only protects against 4 strains of the doggie cold out of 400 strains. He gets his 'annual' rabies shot ever 2-3 years, as papers done by honest vets in France certified it's actually good for 7 years. Follow the money again!
P.S. Speaking of Gator, I found him laying under the desk where the incubator is. He's prone to do that when eggs are in it, like he's waiting patiently for something. He's also prone to lay next to the brooder when chicks are in it. Such a babysitter!
It was heartbreaking to go out to open the doors and find a beautiful rooster sitting on the roost, head hung down completely blue from hypoxia and gasping for breath because of tumors in his lungs. Or watch one struggle to eat/swallow and find tumors in his throat and neck.
The hens just wasted away to skin and bones, developed crop problems, seizures. Then died. I got to the point where I was afraid to do keel bone evaluations on them. Afraid that I would find the walking skeleton symptoms that were so synonymous with end stage MD.
Vaccinated birds saved my flock and saved my hobby. It was a chance and like you I'm not 100% sold on Marek's vaccines but something in it is keeping my flock alive....so far.
For the past two years I haven't seen signs of the killer in the corner. Oh, it's there. I know it it but between bringing in vaccinated chicks and local resistant flock, my hobby is surviving.
Gator sounds like our dog Buck. That boy goes into his Border Collie crouch outside the coop door when I do chores out there and keeps his 'chickie birds' in the coop if the door is open. He loves those birds.