Problem with my ex and best friend?

[Pierce]

Alright I'll try to keep it as short as possible. Me and my ex girlfriend just broke up about a month ago after dating for 1 year and 3 months. She wanted to break up because she said "we're heading into different paths of our lives and it would be best to stop now." She claims that she still "loves" me and hasn't lost interest. I'm currently underway with firefighting and she's in nursing school. I love her dearly and thought she was the one for me. I thought the relationship was going great but guess not. Now to the main focus.....My best friend who lives 4 houses down from me is good friends with her (I met her through him). Before I started dating her I talked to my friend to make sure it would be okay and wouldnt come in between our friendship. I didn't know if he had feelings for her. He said yes i could and appreciated me going through him. Later out I found out he was pissed that I started dating her. Then I heard that they had hooked up before in the passed (not sex). So now that shes not with me, my ex has been down at my best friends house just about everyday and stays tlll 3am. she even stayed the night there when we broke up. I confronted my best friend after a couple weeks and told him how much of a bad friend he was being since he didn't even ask me how i felt with her being down there all the time. he ended up lying to my face 3 times that day. he would ditch hanging out with me to be with her. Now he knows how much of a dick he is being yet he wont even look at me when i drive by. He goes everywhere with her cause I hear people telling me everyday how they're together. Unfortunately he is now my EX best friend. I want to beat the shit out of him. And my ex has unfollowed me from twitter, instagram, but not facebook....

What I was wanting to really know is what should I think about this situation? Should I say fuck it and never talk to him again? What about my ex, should I try to talk to her even though I'm hurt and still love her to death?
What would you do in this situation???