First of all, my sincere sympathy for the pain you are suffering.
What you are finding out the extremely hard way is that the end of a long-term relationship is rarely straightforward, with a nice clean break, there are issues that trail along and dip in and out of your lives, especially when children are involved.
What you long for is the familiarity and security of the relationship you had, and that is covered over completely by the panic and insecurity that consumes you during this horrible period of change.
Looking objectively, which is a luxury you do not have, your husband has moved on, sadly to someone so physically close, and you are struggling to accept that.
What you want is for everything to be how it was before things went wrong, and sadly, you have to accept that you are not going to get that back, it is gone.
So it's pointless to hang on to a life-line that has nothing on the end of it.
What you must do is work with what you have, which is your children, and yourself, and start looking at rebulding your life with them.
Your strong feelings of love for your ex may not be as they appear - they may be the longing for peace and security and an absence of this pain, but that is not the same as loving him in a way that will let you get past this situation, even assuming he wants to, and evidence suggests that he does not.
If you start using your strength, which is there but well hidden, you will start to accept this situation, painful as it is, and that is the first step towards moving on without him.
He is embracing his 'new love' wholeheartedly because that enables him to try and forget the confusion and pain he is feeling - that manifests itself in his hostility and mixed messages.
I wish there was an easy and quick way to get past this, but there isn't. It takes days, weeks, months of pain and upset, but every day is a day further away from this initial shock and upset, and you will get past this, and be a stronger person for it, impossible as that seems.
Pull friends and family close, keep intreraction with him as minimal and impersonal as possible, and look to the future - you do have one, promise.