Firstly I want to tell you that I think that you have conducted yourself with strength and dignity. I applaud you for that and take my hat off to you. If you can conduct yourself as you have in one of the worst possible times of your life, you on the first step of being the strong independent woman you didn't know you were.
It's going to take time, maybe a long time to feel 'normal', so accept it and take care of yourself. Your DCs are old enough and probably all have a phone so let them communicate or not with their father. My dcs were younger than yours and it hurt like hell to see them put in on a pedestal, even when he had let them down again but they are both in their twenties now and they can see for themselves what a wanker he is.
As for the OW - wow she sounds like one crazy lady. Wtf, who does what she did outside your house and with your DCs!! He's stuck with her crazy now! Throughout your posts you have come across as a genuine, kind and thoughtful lady who clearly loves her dcs and before this, her husband. Now he's got an unhinged drama queen, who clearly cares little about anyone but herself. They were both on an affair site and clearly went ahead with the encounter and they both know what each other is capable of. Every time one of their phone pings, or they are on the phone, the other will wonder if they are cheating or back on that site. Don't think of them all romantic, think of the reality of their situation which is based on lies, secrets and decept.
I hope that they stay together for a while yet because I would love for you to get your sass and strength to tell him to fuck off if he comes back. I want you to know your worth and know that you are better and stronger than both of them.
Take care and just do one day at a time. Keep telling yourself that you are a strong, independent, kick ass woman and you will look back at this in the future and pity him and thank him.