You are doing the right things to protect yourself and your children from his behavior and you are doing a great job holding strong. I think some doubts are normal - I know for me whenever I have set a boundry I always waffled around inside and felt about as strong as jello. Practice does help, you get stronger as you have to repeat things over and over. You held firm today and did not let the manipulation get to you - tomorrow you can do the same.
Just keep doing those next right things and keep the focus in today on what is best for you and the kids. You don't have to solve all of your problems or know all of the answers at once.
:ghug3