You say, "She stole his youth and made him miserable..." However the truth is each of us chooses our own friends, lovers, and spouse. He was with this woman because (he chose) to be with her. There is no getting around this fact.
The next thing you must realize is the only person you can (control) is yourself!!! Whenever we attempt to control others and they don't behave as we want them to then we become frustrated.
Anyone that has been in a relationship for 8 years is likely to remember their ex's birthday. It's not a big deal to get an e-card or a birthday email from someone you spent a large chunk of your life with.
Insecurity is just another word for fear. No one wants to think about someone "waiting in the wings" should they mess up. We long to be able to "relax" and have some breathing room to stop being at our best . (The truth is there is always someone who would love to take your place). We just normally don't know who that person is.
It sounds as though your man is NOT a "rude" type of person. Therefore he is not likely to become rude to his ex just to satisfy you. Is this a "deal breaker"? If it is then you should get out. If it is not then you have to learn to accept your man as he is and trust that it's you that he wants.
If you continue to bitch and complain about the situation while his ex continues to be "nice" to him then you must know people would rather be around people who make them feel good about being themselves. No one wants to live in house full of friction.