My dad is creepy to me and my gf

My dad tries to emasculate me in front of my girlfriend. this is something that has been bothering me for a long time.

I am an 18 M with a 18 F girlfriend. My dad is 50.

My dad provided for me when my mom took off years ago. But he is a real asshole in numerous ways very bad temper, binge drinking, narcissistic tendencies. I am trying to get out of the house by the New Year.

My dad is a really big, muscular guy who is really skilled general contractor. I always was kinda proud of how big and tough he was and a little jealous I am kinda short and chubby.

This spring I had my first long term girlfriend and at first my dad was super proud and supportive.

This summer things changed and he has become mean, clearly jealous I am happy and tries to low key emasculate me and flirt with my GF.

Nothing ever overt or really creepy but, just wearing extra tight shirts around her, making sure he always talks to her. He makes this little comments about how cool her hair color looks. It is hard to pin down but it is flirting.

He also pokes fun at me, like asks if I have enough money for the movies, or tells me I could stand to lay off on the ice cream or Slurpee.

The other problem is my GF admits she is uncomfortable but does nothing in the moment and gets flustered and upset when I tell her I think my dad is creepy with her. She does not even want to talk about it, she just says she thinks my dad is flirty and laughs it off or makes fun of him.

It has killed my confidence and sex drive now too.

I have no clue what to say to my dad and I told my GF that I am just going to stop having her come over when he is around.

I know there is something off here but no clue how to fix it.