I am sorry to hear that your dog got so much marijuana. My name is Rebecca. I am a veterinarian and will do my best to help.
There is no antidote for marijuana, and since it has been 4 hours since he ate it, it is too late to make him vomit. It is good he has vomited, and may have brought up some of marijuana.
Was there any chocolate in the bar? Chocolate is also toxic to dogs.
We usually just do "supportive care" for dogs that got a lot of marijuana. If they are really comatose, IV fluids may be needed to maintain hydration and blood pressure. If his gums are pink, if he will take liquids to maintain hydration, it is mostly a matter of just waiting it out.
If his gums are pale, if he is so sleepy you can't waken him, he may need to be on IV fluids. It is not common for a dog that ate marijuana to be hot. Can you take his temperature? Normal is between 101 and 102 by rectal or ear thermometer.
Let me know what other questions you have.