aggjc23

1. You can file anytime after you get married for AOS. You do NOT need to file by that date at all, in fact many people file after the 90 day mark to ensure that they have documentation. There are no repercussions for filing it late at all, and you filing it late will be forgiven. Just be advised you will be out of status the time after the 90 day mark until you receive your NOA1. 
2. Sorry I don't know what to say about this.
3.  You handed everything over when you arrived at your POE, so you don't need to fill out anything in regards to that as long as your medical was with in the last 6 months. 
 
 

Yes, an I-864 from the USC petitioner is required. An I-864A is for a relative that is a household member joining the I-864.
http://www.visajourney.com/content/k1k3aos

Anything not recorded on the visa medical form must now be put on an I-693 by a US civil surgeon. There are separate instructions to the form that you need to read telling the pages you need to submit. The instructions explain a K1 does not have to complete a full medical exam but you still need the shot page done. The problem you may encounter is a civil surgeon who will insist you need another exam. Or they may say they won't do the immunization page unless the do a complete exam. Call around and ask prices before you pick a civil surgeon.
 
You did not turn in a form I-693 at POE, That form is only used in the US. But yes, your medical exam results were turned in (and they lack needed shots). You still need parts of the I-693 filled out.