Welcome to the Wefugees community and thank you for your question.
It's true that you can't go back to your home country whilst being a refugee because you would lose your legal status automatically. As far as I can see, marrying a German and receiving a regular residence permit will enable you to go there without risking said residence permit. But you have to be aware that having only such a residence permit won't make you immune to governmental persecution in your home country. The German state probably can't/won't do much if you get in trouble over there, especially since you are not a German citizen.
Concerning the certificates that are missing: Get in touch with Standesamt and try to find out whether there is a way to get in contact with a German diplomatic representation (e.g. the embassy) in your home country or with an embassy of your home country. Maybe you can get your documents replaced this way. Of course you have to keep in mind that getting in contact with your home country's officials might cause trouble for your relatives that are still living there. So you have to decide if it's worth the risk or not. Also, note that you are not allowed to enter your home country's embassy in person because it would lead to a loss of your refugee protection status as well.
Regarding your soon-to-be husband's taxes: Married couples can do tax return together and save money that way. It is most effective to do this when one of the spouses earns significantly more than the other. I can't tell you if there are other implications that you have to keep in mind. Maybe someone else knows more about this aspect.