Re: how often do dogs poop on a raw meaty bone diet?

he poops like every other day-- maybe.

Yeah, that doesn't sound like enough, but I am no expert, so maybe someone else will pipe up.

he eats mainly beef marrow bones-- 

Marrow is nutritious but it is largely fat.  I would wonder whether he is getting enough protein.  More muscle meat might help bulk up his stool.

a dollop of yogurt once a day or every other day

An additional probiotic might help . . . yogurt doesn't deliver as much enzymes as a supplement.

(how often can i, should i, feed raw eggs?)

I don't remember where I got the idea that two a week was good.  (I have a 22 pound dog, though.)  I must have read it somewhere, but I don't know where . . . plus there are differing opinions on eggs.  I think feeding them the whole egg is good, some think only the yolk is good.  You've probably run into that argument.

He's only been on this diet for three weeks,

Oh, okay . . . this could just be adjustment.

he could just be not getting enough food for a dog his size--

Again, personally, I would think about decreasing marrow some and increasing muscle meat.