The Russian Visa was very simple for me, just get an invitation, filling the form online, then going to the consulate. I think you can technically leave for one day and then come back but in all honesty I do not know how they would react to that. If you have officially married, you can try to see if you can get an extended stay so you do not have to leave after the 6 months mark.
Once you get to Russia, you WILL be checked when going through passport control. They have even become much stricter now. They won't deny you entry, but they will tell you to wait in an area and they will keep your passport. You will probably have to wait sometime there. It can be 15 mins, or it can be 2 hrs. Then they will call you and most likely question you about why you are there, for how long, and can even ask you personal details about your relationship with your Russian partner. I was even asked if I work out and what I do in my day to day one time (they were implying if I was military or special forces or something). Be prepared to hand over your phone (unlocked). You might be taken to a small room or not. In my opinion just be honest about what you will do there. If it makes you feel better, they are doing that not only to you, but pretty much a lot of foreigners INCLUDING Russians that are living outside of Russia and are just coming back to see family or something. I was nervous but I can understand why. And before anyone goes crazy here, we do the same thing here in America, I know multiple people who were taken to a room, questioned and even had their text messages checked, here in the land of the free. Just remember the current political situation and that they have had incidents lately so the security is tight and that is understandable.
Eastern Europe culture is not like western one. They do not smile at random nor when greeting someone. If you randomly smile at someone they will either know you are not from there or think you are silly or deceitful. However, once you get to actually know them they become very happy and warm people. I honestly have not had a single bad experience with anyone there. Even random people I met on tours were awesome. And no one cares that you are American honestly, they might just be curious and ask you a couple of questions but actually many are happy you are visiting their country.
As far as your documents go, I am not sure with 129F, but with 130 you can do pretty much anything online except any official documents you may need to get here but then you upload them online either way. You only take the physical ones to Interview. But in all honesty as what @OldUser said, you need to have a stable address here in the US, don't count on mailing stuff back and forth as it can take a long time and I don't even know if its reliable. It looks like you haven't studied the 129F enough. Go through all the steps in the USCIS and travel.state.gov sites and become well acquainted with them in what you can and what you cannot do.
Feel free to ask any questions you have.