I hope someone else can suggest methods of turning an outdoor cat into an indoor cat because I have tried and failed. In my personal experience, once they've had a whiff of the outside air and they know what it's like to roam and to patrol their own territory, there's no turning back.
Any cat I've ever had would not follow instructions to stay inside if they had ever been outside. There was no half way. If you open the door a tiny bit, they get out like greased lightening. If you think they can sit on the back steps with you and stay there, think again because the minute you turn your head they're off.
I have enjoyed taking cats for walks on a leash at the beach and one cat liked to go hiking in the woods, following me around, even walking across single log bridges over brooks. But be very careful. I lost one beautiful cat because I took him in his carrier when I went to visit someone and he got out of their house and got run over.
Just don't give your cat any freedom outside if you want to keep him and are not sure of the safety of the area because they do not think. They are animals who revert to their natural instincts (roaming is one of them) and it is easier than you could ever imagine to end up minus one cat.