Move as soon as you are able even if in the same town at least you would have new neighbors. Placing Momo will be a difficult decision for you and the quarantine may be a better option than leaving him with people you don't feel good about. Will they allow your visits in quarantine?
Eat your junk food where he cannot see you and eat healthy foods with him.
I understand you may not be able to order from these folks but they have some lists of suggested items to sprout for your bird.
Sprouting for Birds
http://www.sproutpeople.com/seed/birds.html
Also place his familiar cage in a high place, perhaps on the roof with food & water, also viewing the neighborhood from up high can give you a better chance.
Another hint is to pretend to eat the food you want him to eat and make yummy sounds to get his interest. You can offer him some on a spoon sometimes that works well.
Please look further on this site for different recipes of very good foods for your Grey that you can make for him. Pellets are not required. Look into the section labeled bird food here is a link to make it easy, you will find some for beans, lentils & grain with veggies and fruit that are very complete nutrition and not difficult to make. Sticky: Simple Grey Recipes/Cookbook