You can file any time after the 1 year period. You don't have to file as soon as the 1 year is over. It's just that you can't file during that 1 year period. Don't worry about filing now. You aren't late!
You should definitely consult with an experienced immigration attorney who has knowledge of how criminal convictions impact immigration status. At best you may be given peace of mind. At worst you may find it is an issue and there may be measures you can take to remedy it.
A petition can be revoked until you get your green cards and after that only if there is evidence of fraud in the process. I wouldn't worry too much about this. Your aunt is financially responsible but that is a contract with the government and it doesn't give her power over your status. Sad from a family perspective but I don't see anything to worry about immigration wise.
No you don't have to use that envelope! They always send one and it is almost never big enough for the documents they ask for. Forget the envelope and send your response package in a manner that you can track. Make sure it reaches before the due date. Good luck.
There is no guarantee for the time frame. Your options are the K-1 as my colleague indicated, or the K-3 if you marry first. If you are properly represented by a competent immigration attorney experienced with these filings at least you will minimize any delays because the filing is not done right. Beyond that it is in the hands of the government.
If your case is denied the notice will clearly state that it was denied. The notice you got suggests that you don't qualify for the benefit sought but as you said this is another RFE and the USCIS appears to be giving you an opportunity to rebut their presumptions. As you have legal representation your attorney should be able to advise you on this more specifically.
In my experience birth certificates are required independent of being evidence of citizenship and the passport may not compensate for the fact that you don't have it. Go to the interview any way and if the officer really wants to see the original he/she will give you time to submit it. It ill delay the decision however.
You should consult with an immigration attorney experienced with asylum cases to see if you qualify. You will have to show that you either suffered past persecution and/or that you have a well founded fear of future persecution. There are other requirements too that will have to be proved.