Stillcrying
As I've said before, I'm appalled at the situation your selfish husband and friend have created and feel terribly sorry for you.
It will get better, as other posters have said, and you need to try desperately to cling on to that. It is a pretty poor sort of comfort, I acknowledge, but it really can't get worse than than this.
I've been through a bad time too, and I understand the physical pain thing. It was a shock to me - I suddenly knew what it meant to have a broken heart. A broken heart actually hurts! But that too will get better in time, impossible though that might be to believe at the moment.
I can understand how horrified you must feel about the children going to the OW's house. It is an outrage against everything that is fair and just and I can imagine that it would feel like the knife turning. But I think that it is the lesser of two evils.
In order to heal yourself, you need to establish your own space with your own boundaries, and to get rid of him from your house. And if that means the dc going to the other house, then so be it. Maybe focusing on them and on what is best for them (in the circumstances) is the best way of dealing with it. You're right - they can't stay out of the house for hours. And you walking the streets has to stop. I can see how it has come about, but I feel terrible at the idea of you having to do that. It's not necessary. You need to make your own safe nest in your own home, to forge your own life and start to get better.