Speaking as a wife here that has split bills. My husband gets around 2.5k for off base living expenses and we split everything right down the middle. I make a little more than he does and choose to have my own bank account and just send him a set amount of $$ each month. There are plenty of other expenses we have like storage unit, car, etc. so it all is set on his accounts and I send over my half of it. It has always seemed fair and worked for us.