Today is the day! Good luck.
Sometimes hobbies can be hard for someone with the kind of drive you've mentioned. I would volunteer at places, but also see what kind of skills you can work on where you can work toward an end product and feel that the time is "productive". Some people just need to see a tangible result of their work.
Take a ceramics class. See if there is a glass blowing studio nearby that has lessons. Try woodworking (some community colleges have classes so you don't have to invest in all the big equipment--planers, jointers, shapers, lathes, etc). Try quilting (not seen as a "man's hobby", but there are many men out there who quilt. My grampa and great grampa were two of them, and as old farmers, they were as many as you can get...)
One of my favorite quotes is "If your dreams don't scare you, they aren't big enough". Looks like you're good there, and making the big dream happen will probably feel really good once you have a chance for it to all sink in. Leaving a bad job is like having a light switch flipped. It really is amazing what it can do for your health and happiness.