DesertStorm

I thought the game was easy...even on crushing. The only advice that I can give you other than the information you have attained on your own is to stay in cover as much as possible. Master stealth, you can avoid a lot of damage by using stealth kills. Finally and my most beloved tip HEAD SHOT, HEAD SHOT, HEAD SHOT.  
 
P.S. the pistol may be more powerful than you think.