Hi John,
A lot of people can't always get the search function to work, so its ok!
1. I don't think you would need a waiver for that. It sounds like something minor that was corrected. The only thing you SHOULD need is the medical record from the doctor and/or hospital. It will have to be mentioned, everything has to be mentioned. But it doesn't sound like something you will need to worry about. Let your recruiter fill you in further, he'll have the best answers.
2. Letters of recommendation aren;t mandatory but hey, any little thing can only help, never hurt. If you can get them, go for it. Also, with that, make yourself a resume. Toot your horn a little, make yourself a wanted commodity.
3. Guaranteed anything is virtually gone the way of the dodo bird, they don't exist. AST has never and probably will never be guaranteed. You could score an amazing score on the ASVAB but it will not change the fact AST cannot be guaranteed, at least not now or in the near future.
4. Sure!! Four years could get you there. It is a wait for that rate but still doable in 4.
I hope that helps!

Welcome aboard! You can call and live a message at the recruiting office, you won't be bothering the recruiter. I'm sure he is home watching football, grilling with the family or doing something exciting. So leaving a message wouldn't bother anyone. Best of luck with everything, if you have any other questions, ask away! We'll always try our best to help!
Macie