I went back for school I worked my full time job the I was in and two different internships/fellowships during that time. We had 2 kids under 2 at the time and wife didn't work. It was a rough 2.5 but we got through it.

Trade school sounds like a good idea, or learning a trade on the side. Maybe you will have to jump out of your sales job and take something with funny hours like weekends or evening/nights to get experience in another field. Nothing is going to look perfect but at some point you will have to jump if you want change.

One last point. The passion thing is dumb. Most people don't find their passion from work. Find something you can bring your skills and energy to. The dirty jobs guy has a great speech on this. I wish more people would have gave me this message.