I'm very sorry for your loss.
Well you got Milly as a pup did you not? and Jasper didnt'er attack her right?
I'd personaly give Jasper a bit of time, he may not show it but i'm sure he misses Milly, then I would get a puppy, maybe try and resuce a older pup that won't annoy him as much, like 5 months old?
Hope this helped, if you get a puppy make sure you post lots of pictures!