Well I'm not in the least bit surprised you are weepy. Blimey - what an onslaught. (sorry - got sucked into cooking , bathtime, bedtime etc etc)
Of course you are upset.
Not only the sordid texts, but the fact that while living the life of riley, waited on hand and foot by your mum and dad, he has complete freedom, gives you the runaround by being late, looks after the boys badly (awake at 11pm) AND your parents are downright horrible to you. It's just not fair - not any of it!
And while he is obviously having post-pub sordid fumbles (urgh) with a (no doubt, from the language) young bimbo rather than a significant relationship, it just kind of emphasises that he has been able to freely chuck himself around without a bcakward glance, which is like a slap in the face. And it is 100% possible to be reconciled that you are separated and know that it is the right thing, and yet to grieve for the relationship you DID have, grieve for a relationship of any kind that you don't currently have, and just be sad for the loss of all the good things that there were. It's just sick and nasty that instead of your Mum and dad being there for you, they are rubbing salt into the wounds and making life easy for a man who ill-treated thier daughter.
There's nothing wrong with having a really good cry. Get it all out, be mad and angry with him, with your parents. In the end, you will be the one who is happier throughout your life than any of them.
You ARE doing really well, it's no wonder you are distressed, it's all too much.
But it won't last. You don't have to cope 'well' with everything, you can be upset and go to pieces for a bit. Them gradually, you will feel better, and things will be better.