What should I do with him?

So, my cat loves to be outside, but the thing is hes an indoor cat. And out screen door does not shut all the way so when u leave u have to make sure the door shuts or he will run out. And I would let him be an outdoor cat but he dont know how to fend for himself and he would not know how to get back home. I take him to my grandmas in the summer and he sits on her frount porch but other then that I try to take him out but then he thinks he can go out.. And he has dark fur well he is a maine coon cat so he fluffy.. and when he gets out at night it takes forever to find him. And I dont know how to stop him from goin out. When he gets out i bring him in a spray him with water or i even spray him with water when he sits by the door waitin for someone to come in.. But it does no good.. He likes water except when givin a flea bath and water in the face. He is 2 years old and i just dont know what to do.. I am scared hes gonna get out and get hit by a car.. Or that he will get out and we wont be able to find him.. Please help me.. I cant think of what to do to get him to stop.. If u have advise please tell me. If u dont know dont comment please its a waste of my time.. Thankyou..