How does one deal with the emotions of being violated by a friend, particularly when this is impeding one's ability to function or invest myself fully in repairing my relationship with my long-term partner?

First, some background. I was working overseas under difficult conditions for the past few months and became very close friends with another person in my house. An intense friendship formed quickly and I felt an a strong emotional connection to this person, likely furthered by the extreme emotional vulnerability I was feeling through the course of the summer.

Nothing happened myself and this person for the first 3 months except (what I perceived as) a very deep friendship. My long term (9 year) relationship back in the states wasn't going well - have barely talked, not feeling an emotional connection, bad sex life before leaving, only talk about his life, etc.

By this point, I am having increasing romantic feelings towards my overseas friend mostly borne out of the emotional connection/solace that I feel from that relationship. This friend and I go to another city for meetings and I end up spending the night cuddling with my overseas friend, but nothing else. 2 days later this friend and I are talking and moved onto meetings in another city and I say, "thank you for not taking advantage of me in City X, you easily could have and I appreciate that you respect me enough as a woman and a friend to not push me to go further."

Fast-forward a few hours later, he is pressuring me to have sex (with rationale that is now laughable) and I end up capitulating after a while. This is the biggest mistake of my life though things only got worse from this point. This "friend" abandoned me after we parted ways at the end of the summer, mocked me through a pregnancy scare, and has been relentlessly cruel in attempts at his own self-preservation/assuaging his own guilt, completely dismissing me and any attempts at talking through this.

I don't understand how someone I considered one of my closest friends and one of the people whose attitudes towards friends I deeply respected could do this to me. Fast forward a few weeks and one near-miss suicide attempt and I am back in the US with my partner and working at the same university as my "friend" (we have to interact professionally for at least the next three years). The one bright spot of this whole disaster is that it has made me appreciate what a kind, good person my partner is and renewed my will to work on that relationship. Unfortunately, the ordeal with my "friend" left me feeling extraordinarily violated and taken advantage of.

I was not raped, but I still feel that this friend took advantage of my emotional vulnerability and half-formed feelings to have sex with me and then is demonizing me as a means of self-preservation. I just want this to end. I want to work things out with my partner, but the things that happened with this "friend" are destroying me and consuming my emotional energy.

I sent an apology and took responsibility for my portion of mistakes that were made to my "friend", but feel that he just took it as me pardoning him for his terrible actions. I love my partner and feel doubly guilty for both betraying him and continuing to be destroyed by the hurt my "friend" has caused. I have not yet told my partner, but intend to very soon.

So my question is, how does one deal with the emotions of being intensely violated by a friend such that they are no longer impeding my ability to function or invest myself fully in repairing my relationship with my long-term partner?