Dont ask him, more than likely he is skimming your bag thats why you havent met the dealer.
Do you know where the dealer lives?
If you do best bet is to go talk to him be upfront and honest.
Say man I dont know you but I have bought bud from you through a friend for(however Long) and I would like to just come to you from now on by myself.
I think my friend is skimming my bag and I am tired of that shit tell him you are no cop and dont ever wanna cause him trouble you just wanna buy weed.
I bet you from that day forward you would have your own dealer.