Not sure how I missed this thread, but I did!!
Bless you for taking this wee mite, but you are quite right, you cannot take them all and there is no point in taking on more than you can handle at the expense of the ones that you have, so stay strong!! The other thing is, of course, that, hard though it is, if you take the "problems" from these irresponsible breeders, you encourage them to breed more.....
He is a Black Dun, btw, erroneously called "blue" Dun which is a descriptive, not genetic, term.
Translated it is "Grullo"
I am afraid you are going to find, in the spring, that you do have a few nasty surprises under that fur, but it does not look as if it is going to be anything that you cannot cope with. Just be prepared, that's all, and do not expect your Vet to know anything about dwarfs, either, I am afraid they are pretty much at sea on this subject.