Forgive me, I've only read the first page.
I thought I was the only one who went through these "phases" and made my wife's head spin.
For now, she is your girlfriend, not your wife, so you don't necessarily
have to obey her.
After 4.5 years of marriage, my wife is now used to my phases. Her opinion is that if it doesn't hurt us financially, she's OK with it. She has gotten used to the fact that I'm not a "normal" guy. Sometimes, that's for the better, and sometimes, it is for the worse.
She has found out through talking to her girlfriends that she prefers that I participate here and on other fora than be at bars, drinking, or spending every spare moment watching sports.
Other than shooting, I also do motorcycling, woodworking, snowboarding occasionally, video games. (Game Boy DS, lately) She was not comfortable with my motorcycling (her being a doctor) but she got used to it, and now she loves it. She even suggested we trade our Kawasaki Concours up on a Yamaha FJR, because it is faster. She feels safe with me now.
I asked her to open her mind and try shooting. She doesn't like it as much as I do, but she likes to shoot 22 with me from time to time and will grudgingly practice with her 9mm Hi Power.
RC planes, she wound up liking because our little dog lost some weight chasing them around.
Woodworking, she loves. (Once she got over me spending thousands of dollars on machines) I have a jewelry chest in the works for her now, and I made our nightstands in the Craftsman style out of Ash.
So my recommendation is to encourage her to be open-minded. Remind her that you will not move so quickly that it will hurt the two of you financially, but also that you don't necessarily need her permission to do everything. You don't want to end up whipped.
This is the cornerstone of our "play money" system. We do the budget together and decide how much play money each of us gets. What we spend it on is criticism-proof. She can buy shoes, purses, cosmetics, clothes, without fear of reprimand from me. I can buy guns, RC planes, woodworking machines, and motorcycles without fear of reprimand from her. I don't know if you need to do this yet, as you are not even engaged.
It helps to find an unselfish hobby to supplement your selfish ones. (for me, it is woodworking and motorcycling)
It seems like the bigger issue is that she thinks you might be turning into a scary militia-man.
Convince her that you're not, and that this is just a hobby. Convince her to think of exercising your right to carry is just like wearing seatbelt. Yes, you probably won't ever need it, but if you do, it will be DAMNED good to have the option of drawing it. Also remind her that there are some very bad situations that are avoided just by drawing a gun. She will think you're paranoid but may accept it. If she is so sure she wants a "normal" guy, maybe it is time to let her go.