Here's what you should have done, for all those contemplating something similar:
Applied for citizenship. If you have had a green card for 7 years, you are eligible (after 5 years for all cases, living in the U.S. 30 months in the past 60).
Become a citizen.
Apply for a K-1 Visa for your fiance.
Ensure he doesn't violate a single immigration or other law waiting for the K-1.
Get married in a year.
Convert his K-1 to a green card.
Here's what you and your boyfriend did instead:
Your fiance overstayed his temporary 3 month visa, flagging him with the USCIS (I'm uncertain why you believe there is doubt about this: he either did or didn't). He also illegally earned money while in the U.S.
He left the country, meaning that he would encounter the USCIS if he returned.
He returned in a manner that indicated that he meant to stay, while arriving on a temporary visa, indicating an intent to leave on expiration. He didn't have a return ticket, and has a fiancee in America he was marrying. This violates the doctrine of dual intent.
He admitted all of the above.
I don't know why this is shocking to people, but if you flout laws in America, the country doesn't treat you well. He's lucky to have been deported with a five year ban.
Take your story to www.visajourney.com. I was active on the community, and they can help you further. You will also need a good immigration lawyer, and this will get expensive. It would also bolster your case to become a U.S. citizen as quickly as possible for the rights that you will need.
If you don't like these options, it's time to look into moving back to Russia to be with him.
Good luck.