Potter3

Thank you so much for being so supportive. I really appreciate it. 

Honestly without his mom being in my life I would’ve gone crazy. 
 
it’s the worst times that anyone can ever experience, especially when it happens out of the sudden! 
 
god rest his soul, I know that he’s watching over us. 

The list of documents you mentioned looks good. His mother could also submit an affidavit like the following example:
 

Copy of taxes is not required. The "Evidence of the Relationship" is in a case-by-case basis: https://www.uscis.gov/sites/default/files/document/forms/i-751instr.pdf "Submit copies of documents indicating that the marriage upon which you were granted conditional status was entered in “good faith” and was not for the purpose of circumventing immigration laws. Submit copies of as many documents as you can to establish this fact, to demonstrate the circumstances of the relationship from the date of the marriage to the present date"
In my opinion, attorney not need. It can be DIY. If you have any questions other users here in visajourney may have relevant advice.

For immigration it's not an issue. Couples sometimes file Separately for financial reasons.

Yes, send a copy of the same type of documents you had at recent interview. Like you mentioned, there's probably a few even newer documents (I.e. joint bank statements, etc.) in the short time frame after the interview so also send a copy of whatever you do have.

If you have Wills, durable & general powers of attorney, and similar estate documents, these go a long way as evidence.

Thank you first for your replay eandEandH0904 and yes I did a lot of search here but I just want to make sure that everything will be ok .. and yes we've been together for 1 year and we did met and took a lot of photos and he sent his papers now from the u.s and we're waiting them to schedule us a meeting .. but I wanted anyone from here had the same issue to just know what he did .. specially that I need some stuff related to the military stamp. 
Thanks a lot again for your replay EandH0904.