I know it's difficult, but try not to over analyze what he's saying and doing. Holidays tend to bring out some unusual behavior w/them.
Solo Partner is on our recommended reading material thread.
Even though your dog has crossed the rainbow bridge, you still have many fond memories of the time you spent w/your pet. However, if your sister brings her pup, you can play and love hers during your stay.
Keep the focus on you.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.