We watch the Dog Whisperer show on National Geographic channel. They have had a few shows where a human will have died or been very ill, or a dominant dog passed. Cesar Milan will go in and say the dog wants a pack leader (calm assertive attitude - not angry or upset), and in the absence of that will display different unwanted behaviors. Since you've been in a weakened state (grief), he may sense a void. Was your Dad his pack leader? In a human-run home, it should be the humans.
One of the no-no's I'm guilty of is giving affection when our Jackpot is not in a calm state. Apparently that reinforces the behavior (whining). I've said for years she has me well trained. LOL!
Nanc or Mimi or one of the other dog-savvy folks could probably be more help.