During my active duty career I had the fortune to pass through Germany several times. I never had a bad time in that country! Try and pick up at least a little bit of conversational German before you go. Most Germans speak English, but it set a good tone if you try and open a conversation in German. It helps quell the ugly American stereotype.
x2 on getting your BF's passport early. It does take a while these days.
I've lived on ramen noodles and 4 for a dollar Mac & Cheese for extended periods of time with no ill effect. Crackers are cheap and can be spiced up with PB&J. Rice and a 98 cent can of field peas with snaps is good for you, dirt cheap, and easy to make.
Shop the dollar store for all your non-perishable food items as well as cleaning supplies.
If you own a bike, ride it when you can instead of taking a vehicle.
Enjoy Germany!