I also have a Jenny Lind crib which I did not use until my little girl started sleeping through the night. It was the first night I put her in the crib to sleep. I went in the next morning and she was still asleep but her one leg was also between the slats sticking out. Since she was only a couple months old, she did not have any bruising or trauma like your little one did. I also had the bumper pad in the crib and it didn't prevent it. But at 18 mths. of age a bumper pad would be a danger. Dylan could use it to climb out.
I know the feeling of having a child's leg stuck. When visiting my aunt my daughter got her leg stuck in their chair. She was three at the time. We had to get hand cream and cream her leg up to get it out. We worked on it for about five minutes and it was one of the scariest times in my life. The other scary time was when my husband fell down the steps holding her. He did a wonderful job of protecting her but he had suffered a pretty good back injury. They basically slid down on his back and he had her safely in his arms.
I'm glad Dylan is okay but as a parent I have to tell you there are going to be many times when you are going to be scared, expecially if you have a little daredevil for a boy. Hopefully Jenny Lind will change their cribs after seeing the pictures.