Save up all your pennies...for ages.... buy a stompa. Don't tell him. Then unleash death.
Put a clown doll with light up eyes in his bedroom while he's asleep.
Put a baby monitor under his bed and make noises in the night.
Put a hair on his toast.
Hide some fish in his curtain rail - won't find it for ages and will stink of fish...
Swap armies for a game. You know what you can do with your army already, learn his. Then you can
A. see if you're being done
B. See what he'd do with your army - if he's cheatin, he'll either have to let you cheat and win, or say 'derp, I've been getting x rules wrong lately'
or next daft thought -
C. He'll change the rules to suit the orks - in which case you'll see what kind of player he is. And don't just not play him if he's changes rules - take the gloves off! Change every rule in your codex if you have to!
Stick with the orks
- as far as I know, there is no way he could kill your warboss in a truck in one shot. You shoot to blow the vehicle up. You may take a wound from the explosion - It's not going to kill you. All shooting is resolved at the same time so he can't fire a battle cannon etc and then sponson you to death either. Unless he can get your warboss in the open on his own he should find it hard to kill him.
At least till 6th when everything changes