Oh sweetheart, I completely understand what you are going through more than you will ever know.
I met a man in 2018 and thought he was "it" and I regret not doing exactly what you did the second I found him on apps. I stayed for another 4 years looking over my shoulder. I did leave him about 3 years in after he was abusive towards me, but he came back and pulled out all the stops for me.
I ended up buying a house with him, moving back in with him, he even proposed to me and I never checked his phone again because subsciouscly I decided what I didn't know couldn't hurt me.
He would uninstall all the apps after he'd finished chatting and give me his passwords to make me feel "at ease" because he loved me so much. So much of what he said and did was amazing but it was all completely fake. The mask slipped when I questioned him though, he didn't like that.
In May last year I just got up and left our house, he lives there, I live in a room share. I've had to mourn and am still mourning all my dreams and hopes and the fun times we had, the things we said, the affectionate times we had. It was all a lie from his end, all of it was fake.
One of my friends who lives near our house told me that there was a girl going there regularly and I found out it was his 24 year old colleague, he's 47.
I'm in a room share, single, can't bring myself to date anyone even 9 months later and he moved on within weeks. My friend even helpfully sent me a photo of her car which broke my heart. When I went to get some post from our house while he was out I found a sex kit on the floor. I had to sell all my beautiful furniture to pay off the debt and dismantle my whole life. I'm now in a battle with him to get the house sold, which he won't buy me out of and tries to block me progressing to a sale.
I wish I had done what you did and cut him out as soon as I found out. The grief is up and down and it's so hard to mourn the loss of dreams you had, a person you thought you had but never really did. It truly is traumatising and hard.
I want to assure you that you are getting there though, you are extremely strong and resilient even if you don't feel it. There will be a happy ending for you.
For him however: Yeah he'll be doing what my ex is doing, dating others and treating them all the same as he treated you, but as my counsellor says to me, they are deeply deeply unhealthy people and they will never change or accept responsibility because they are just not well people. There is something inherently wrong with them to be able to do things like this, and it seems impossible to get to grips with when you were with them and loved them, but it's the truth.
You handled this whole thing like an absolute pro and honestly things will dredge it up again occasionally but you're going to get through it and you're going to be ok. He is not living his best life, he never has. He is mentally incapable of forming authentic attachments... and honestly you have to feel sad for those kinds of people in a way.
Don't get involved in any of it, just move forward. Don't warn other women because they'll either accuse you of jealousy or you'll involve yourself dealing with him again. Just stay away and focus forward girl.