Love, love and more love BUT stick to your boundaries no matter how guilty you feel dont try and compensate in other ways. Children love structure and they love rules, they also live to push those boundaries its our job to keep them in place NO MATTER WHAT THE CIRCUMSTANCES.
He is able to tell you he hates you, simply because you are his safety net, he knows that no matter what he says and does to you, your love is unconditional. He cant vent like this with other people because he doesnt have that security with them. As hard as it is to hear, its actually a testament of the trust he bestows in you.
Be there for him, talk about things if he wants to, let him know you know he hurts sometimes but that the sadness wont last forever. Let him know he is loved totally and utterly even when he says those awful things.
A journal is a good idea or ask him to write letters to you and dad explaining how he is feeling. He could draw pictures when he is feeling down just to get the feelings out of him.
Its a tricky road, guilt kicks in and is no use to anyone, least of all you and your children. Its hard for you, its hard for them but it wont always be that way, its a matter of time and adjustment for you all and you WILL adjust.
Explain a smuch as you can, let them know its normal to feel angry and sad sometimes, tell them you also feel like that sometimes.
I have found with my 9 year old honesty is the best policy. we went through a rough patch 'I want to live with dad' OUCH! But we got through it and we are probably closer than we have ever been now.
You and your children will be ok, have faith and remember that guilt is nothing but destructive.