What type of hinges did you use? I used strap hinges that were roughly 6" on the jam and had about a 10" ******** the doors pictured below. The hinges I used took #12 screws and I used every mounting hole. Being more of a mechanic than a carpenter I tend to over build stuff so my doors were heavy. The were 7' high and 4 1/2' wide and I think they weighed in around 130 lbs a piece ( I built them like a 2 x 4 wall with diagonal bracing, a ton of screws, T&G fir on the outside and veneer paneling a little under 1/4" on the inside. They didn't sag and the hinges didn't suffer in the 6 years or so before I moved. I used cane bolts in the bottom and drilled into the concrete as was suggested earlier to lock the doors from the inside. I also put small slide locks at the top to keep them closed tight against the weather stripping as I did heat this are area in the winter. We were in a very windy area, usually blowing right against these doors. I used some antique barn windows and left the sheet of vapour barrier intact over the windows to stop the wind.
Excellent job on the structure repair. I think I'd have gone the same route, I'd enjoy character of the old building more than the benefits of a new one. I'm also a lot better at fixing something that's already there than starting form scratch. From a safety point of view, that is something you have to assess and reassess as you go, but it stood for many years and survived many storms the way it was. Everything you have done has made it stronger in the end so as long as you take precautions while you work it can only get better. With a big budget you can do nearly anything, often with little or no effort... But that is a building with character that 'fits'. It would cost far more to replace it with a new structure that 'fits' as well as that one. Good job.