Kboys, I still have these moments. Amy55 has a thread going on that speaks to this as well. I have random moments, times when I'm really happy and content and all of a sudden I'll have a memory like you're describing, an awful memory that contrasts so horribly with the peace of the present.
It does get easier. Three years on and I can just shake my head now at what I put up with and send a positive thought his way along with the hope that his current wife and stepdaughters aren't experiencing what my boys and I did. I am still struggling to forgive myself for what I put the kids through. As an acoa I *should have* known better, but I really didn't until I started working my own recovery.
I think it's a part of your healing. Sending love to you and your boys. I'm glad you all have peace right now.