If that was me, I'd throw caution to the wind, pack the job in and let the devil take the hindmost.
If you're working 10 to 15 hours a day for someone else, in one week, just how much work could you get working 10 - 15 hours a day for yourself? It's a question of motivation and belief in yourself.
A few years ago I was in a similar situation. The stress and tiredness of working like that creates a cloud of apprehension that makes the decision to do something about the situation very difficult. I got a job with a national company doing cradle work and on paper, the wages looked ok but in practise, the goals they set were not achievable and as 50% of my wages were finishing on time..... I stuck at it for 5 long months and like you, I worked 7 days a week.
Then one morning at a job the area manager turned up and started telling me about the need to work faster, etc, etc. All I wanted to do was batter the c... but instead I picked up my gear and walked away.
For a few months after, to say that the missus and me were skint was an understatement. It's amazing what you can do without if you have to and actually, it was in a way refreshing as well.
After the craddle work I made another daft decision and was doing subcontract window cleaning work abseiling but I packed that in earlier this year, not due to the wages but due to the amount of driving and incredibly long hours I was doing, and went back to doing houses and shops. It took me about 3 months to get full books. If I can do that, so can you.
If I was you, I'd dump the job tomorrow and just go for it. All you need is to do is a lot of leg work with leaflets.
(Also, you can get working tax credits and other benefits if you're on low income.)