Have you tried braining? It looks like you're tried everything or nearly everything else. Might just be that your snake won't take F/T and that sucks but you might just have to deal with it. At least he's willing to take live rat pups so you don't have to feed tons and tons of mice as he gets bigger. If all else fails, you can always start breeding rats. I know the pet store I buy my feeders at is willing to take overflow feeders from herpers that end up with too many mice/rats for their snakes.