This will take time to heal. It's a shame you can't afford therapy because I really think it would help. He did betray you trust and it will take time to repair the dammage. There are books that help you learn to conrol anxiety, somebody on PC might could recommed a good one. Try to stay calm around the kids; they shouldn't have to suffer for his mistake. Try taking 10 deep breaths and letting them out slowly before speaking. This might calm the anxiety enough to keep you from snapping at them. Good luck to you.
Gayle