Bright, I think you should have a conversation w/your son about his relationship w/his step father. He may feel a bit uneasy being in the middle, even though he's grown. I do think he wanted to come by and tell you that he was going to the vacation home for the weekend because he knows he had told you something different a while back.
As for your h and the ow, they may have just been friends or fXXk buddies. Keep in mind, when they are acting out, they can have a number of partners or can settle down w/one. It's okay to be curious, but I think you need to stop looking at his FB page for a while. I think it does bother in in some ways and it keeps you off balance just a bit.
I'm also glad to read that your mother has returned home. I'm sure it was an emotional time for you.
Just because there is nothing going on in your life w/regards to your h, that doesn't mean you can't come here and post about you, your life and what you hope to accomplish in the coming months. We like to see posters come here and post about themselves because that lets us know that you are healing and doing okay.
Bright, you are going to be just fine. It does take time to heal.
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.