itsmyturn I am very sorry for the loss of your DH.
You say you got a puppy after careful consideration, but I do not believe you did. For a start, had you considered it carefully, you would have done your research properly and know that buying from such a breeder was a real no no, not least because as you have found out, these sorts of people do not care less once the cash is handed over. Had you have gone to a proper and decent breeder, not only may they have sussed your situation and suggested (after the questioning they would have done) that maybe now wasn't the right time for you, but they would have been available on the phone pretty much 24/7 for support after the puppy had left thema nd you may not have found yourself in this situation. Had you still felt there was no option but to rehome the puppy (that you'd only had a few weeks!) then they would have taken it back and either kept it or found a suitable home for it.
I don't believe that a home with an elderly dog affected by cancer is the best home for a puppy either, at the very least it's extremely unfair to an old and sick dog to introduce a young, boisterous and annoying puppy, not many older dogs in that position would put up with a puppy and I hope to goodness the new home don't suddenly realise that having a puppy isn't fair on their existing dog and decide to 'get rid'.
I am not in the position that Val is in, but I too see people treating their dogs as disposable every single day and rehoming them basically because they can't be arsed to train them or walk them and yet still expect them to be magically well behaved saints. Then, they soon get another dog because they stupidly fail to see that the fault was theirs, not the dogs and they think another dog will be different. It never is... 