What a beautiful dog ! .
( once the authorities get involved, you lose all control of the situation) Since this dog is getting used to you, you might just keep on doing what you have been doing. Spend as much time as you can in his "territory" where he can see you.It will take time. For a temporary shelter, a large heavy cardboard box might work temporarily, just to keep him out of the wind. You could take it to the area where you feed him. (With the snow on the ground you might be able to follow tracks, and find out where he is bedding down, and leave it there too.) I wish you the best of luck with this beautiful animal. He deserves a loving home, and someone who would really love him. And it sounds like you do !