Ohhh My, Villette, I'm so sorry about your hubby. I will keep you and your family in my thoughts and prayers. You are such a wonderful person, I know God has a special place for you and those you love.
About the puppy, I would let him have one. It may be just what he needs to give him an extra boost and put a smile on his face. Maybe you can truly let it be "his puppy" in that he does a lot of the care for it as well. You would be amazed at what joy and fullfillness caring for a puppy can bring to some people.
I have a story to tell you, and it's long, so I'll give you the abridged version: When my grandmother was very ill, she kept pushing for a puppy (not any particular kind, just a puppy) and we were thinking how are we going to take care of her and a puppy too?? Well, one of her friends actually got her the puppy and gave it to her, and some people in my family were really upset. But by the end of the week, she was doing so much better, she was even getting out of the bed to feed the puppy and to let it outside and she hadn't gotten up in 2 months. Then we all wish we would've gotten her one sooner. I truly think that it is that pup that made her turn the corner and fight the cancer and has kept her alive today. I know this sounds wierd, but its almost as if she felt needed by her puppy and that gave her a reason to keep going. Anyway, I guess that is why my response to your questions is what it is.
I know it will be harder for you to care for three than 2, but we never truly know what we are capable of until we try.