I'm by no means even an amateur in this subject. But I used to be an airline pilot, and I'd frequently see people in your situation that either made a career change or were considering it. The salient qualification for their happiness in their career change seemed to be how much money they had upon entering the career. I worked with a retired NYPD Captain and he seemed to be fine with his lot ($17,000 a year salary + his pension which was close to 6 figures), same with an ex wall street guy. The other people that were in their 40s and left only average jobs seemed to be miserable. It always seemed like they would probably be happier by staying in their old job and doing some sort of professional flying on the weekend, flight instructing, banner towing, glider towing, VFR charters, etc.

I'd propose the same thing for you. Why not work as a software engineer on a contract basis, scale your life back as much as possible (get rid of anything like a car that requires a monthly payment) drive an old beat up civic maybe move to a cheaper house (with a nice workspace) etc. And work on the frame business in your free time. There's so many venues you can advertise in these days, and if you're not relying on the frame building to pay the mortgage you can scale up slowly. In a city like Toronto there must be tons of farmers markets and first friday type art walks that you could set a booth up with your wares, combine that with a website and you're in business.

Good luck.