Go ahead and scream! Yell and curse at him too!
Write a letter blasting him for all the things he didn't do, did do, etc... (but don't give it to him). Use it as a means of getting all that emotion out. No more stuffing your feelings!
Have you tried a face to face Alanon meeting for support? There will be people in the meeting that have felt the same feelings when loved ones enter rehab. It is a great feeling to know that you are not alone in these emotions.
As a recovery buddy, please be aware of your natural grieving emotions at this time: anger, denial, bargaining, acceptance, and depression. Your relationship (as it was) is ending, and you are naturally feeling a sense of loss. Notice your feelings and please get help if you feel stuck in anger or depression.
(((hugs)))