Sorry but a clear bra is your only solution, Either that or respray every two years.
Modern quality clear bras do not yellow, need polished and care but can be pretty close to invisible.
Waxing and sealing will not help on road debris very much at all. My JB car was riddled as well and it was polished and sealed every 5 mnths and topped with wax every 6 to 8 weeks and it looked like a teenager with a bad acne case at 170K.
08 E90 335i Monaco Blue Gray Dakota ZPP ZSP Heated Seats CA Step w/Paddles iPod