Hugs to you missingmydad, I am very sorry for your loss.
It seems I was about the fourth sleuth to mention the missing family. I think we are all connecting that dot because there was money involved there also.
As for the girlfriend - is she still in town? Have you talked with her? Did she attend the services for your dad? If so, did you talk to or see her that day? I'm wondering what her "persona" was like? I'm sure you were too upset at the time to pay any attention - so don't worry about answering that.
I agree with you, I think your dad was attacked at the bar and who ever attacked him called someone at your dad's house to open the safe. So... it seems to me that a minimum of 2 people were involved here. If they would have taken your dad back to his house, LE would have found traces of blood and/or other evidence that your wounded dad had been there.
So the question is - who called your dad's house and what phones were used? Did the perps have their own phones? Probably. BUT if not, and one of them used your dad's phone, it would show up on his records. Has LE obtained all records for the cell and house phones? Incoming and outgoing calls? You should check with them. They probably have this information, but you should have them confirm that with you.
I believe LE is smart and that they know what they are doing - however, I also believe that with many individuals involved, it is important that you have info verified and confirmed. One officer might think another is doing something and that other thinks someone else is doing it and it doesn't get done. Or they may have thought to do something, but something else came up, they were distracted and it didn't get done. Asking for confirmation never hurts. They may wish you wouldn't ask so many questions, but the squeaky wheel gets the grease. Persistence and patience are virtures, in my opinion.
I praying that answers are found and justice is served.
Salem