Hello... I wouldn't put him down...
most people here would probably tell you to bring him to a herp vet to be treated.. What I would do, is get as many vitamins and minerals in him as fast as possible. It sounds like he isn't just calcium and vit d3 deficient, but deficient in just about everything.
I suggest getting this
https://www.vitacost.com/morningstar...WWsxoCNi3w_wcB , put it in his water bowl with his water (make sure his water is clean and non chlorinated, like city tap water is). Also get him some other kinds of food, like crickets, and gut load them before feeding them to your toad. Hopefully it's not too late for him, and he'll come out of this