OP, I'm sorry you are in such a sad place. You say that you wish you could fast forward a year or two to a happier place, and I can understand what you mean, but you just have to go through the grieving process for the marriage you once had and the future you thought you had. It's all part of the healing. So be gentle on yourself and go with the flow. Take each day at a time, and accept that it's going to be rough for a while.
I'm nearly three months down the line from ending a 22 year marriage, and I realise when I read threads like yours that I've got off quite lightly in the emotional stakes, I feel nothing but relief and irritation that I stuck it out so long. I should have thrown him out over a year ago. I also realise though that although we physically split in Spring, we actually separated mentally and emotionally over 18 months ago, and I did a lot of my grieving then. And they were really bad times. I was also at the time losing my dear sis to cancer, and am still grieving that loss, and have ok days and awful days regarding that loss. All loss is horrible - but we can't bypass or speed up the process. When you ask how long will you feel like this, all I can say is that you will feel like this for as long as it takes. BUT, it will get easier, I promise.
I think you need to minimise contact as much as possible. You need to get a parent to answer phone from him and then they can put DS on to speak to him. If you have to have contact, make sure it's about the dc and nothing else.
I also think, and this is a biggie - that you are at the mercy of him. What he decides, what he wants. This is wrong. You're his wife and the mother of dc. You need to grab control here, so he doesn't control you and your future any more. So, in a week, or whenever, get some free legal advice, and get a solicitor to write to him to say that you are starting legal separation (or even divorce) proceedings. You will feel better for doing this. It will give you control and make you feel much less vulnerable.
You are hoping against hope that he will have a lightbulb moment and beg you to go back. Honey, he won't. And if he did - then what? You can't erase the hurt he's put you through, you have to accept that this has happened, and nothing will be the same with him again. He's changed, he isn't who you thought he was.
Take care