sorry to hear. i was also in the same position over this past year.
you can make peace and accept that it happened and it can't be changed or undone. you won't ever be able to truly forget. however, the resentment you feel, these complex emotions that are made up of anger and sadness; channel these emotions into something beneficial. use how you feel right now, this anger and sadness, this resentment, as motivation; to move on, show him that he can't hold you down forever, and get to a point in life where what he did to you, and you're pain and suffering made you BETTER THAN HIM; AND SHAPED YOU TO BECOME A BETTER VERSION OF YOURSELF, IT MADE YOU STRONGER. believe me, he may be living life, but dont think for a second he forgets what he did to you. and one day down the line, hes gonna remember the type of person he lost, and the mistake he made in hurting you. and by the time he does, i hope you're FAR BETTER OFF WITHOUT HIM AND YOU'VE USED THE EXPERIENCE OF WHAT YOU'VE GONE THROUGH TO MAKE YOU SO MUCH STRONGER.
for me, i used my resentment and how i feel, as motivation. i used it to drive me to want to do better and move on, so i can be better than the person who hurt me, so i can get to a point in life where they'll know and regret what and who they lost. and i have times where i remember it all over again, and i get sad again; and i also have times where i keep using it as a reminder to force me to keep going. im pissed off, but i WANNA DO BETTER THAN THAT PERSON WHO HURT ME, and the last thing i wanna do is let the person who hurt me, get the best of me and live life knowing he got the best of me and the "last laugh". nope, never.
lastly, this resentment. he's moved on, seems happy living life; you ask yourself, why? why does he deserve to get away with causing pain and heartache just like that and ontop of that, given the opportunity to be happy and live life as if he did nothing to me? why does he have that but not me? and that's completely fine to be stuck on, cause i certainly was. i mean, why do all these people that hurt us, end up getting away with it in a sense? there bad people, yet they get away with it and have good come their way ontop of what they did to us. HOWEVER, i truly believe the pain and suffering that someone inflicts onto another person will come back to get them. the energy you carry, and you inflict onto others, is the same energy that will be reciprocated back to you in life. maybe not now, but down the line in life, it will. it will catch up with him. the people who hurt us are terrible human-beings and their energy and their actions will be the end of them. it's hard to believe that, but i hope you're able to see this one day.
i hope you use how you feel and this pissed off mentality and array of emotions as a weapon and a strength that motivates you to be better than the person who hurt you, as having gone through this experience is going to make you so much more stronger. and the inability to truly forget, as a reminder of what he did to you and how you felt; to further fuel this pissed off mentality to push you to keep going and be the best version of yourself, live life and be happier, and further show him you're better off without him and that he can't and WONT HOLD YOU DOWN FOREVER AND WHAT HE DID TO YOU WONT SHAPE OR CONTROL YOU.
hope this helps in anyway possible and i'm sorry if it wasn't much help :/. take care.