When. he gets too rough, end the game immediately. This is a big punishment because he loves to play. When you stop the game, make sure he knows it's his fault. Say he scratched your ARM, say no firmly and hold your arm. He will soon learn that certain actions on his part stop the fun.
Don't accept bad behavior from him. If he's like this now, imagine when he's a full grown dog with way more strength. This could be dangerous for you or if small children are around. Get help with training him now. He is not the Alpha dog. You are.
Dogs are predators by nature. 'Play' is hunting and protection practice. Most dog breeds were originally bred to either hunt or fight or guard or all the above. This genetic memory remains in most dog breeds and needs to be trained into submission. When to you is 'playing' may be more serious to the dog. It responds to you the way it is genetically programmed to do.