I've been biting my tongue, but can hold it no more.....
A few comments on reading the OP's posts:
You regret your purchase, may not be able to comfortably pay for it and wish to unilaterally revoke your contract; ok, I get it. That's your right, your decision and your consequences.
You've hinted that this is a choice--not a necessity--and offered to submit "financial hardship, or death in family, or illness..." unless they might request "proof" of said condition. Sorry, but this sounds like outright deceit to me. I guess you think that you can lie or cheat with a clean conscience because you don't like their methods? Sorry, but that's not the way it works. Don't sink to that level.
You called the salesmen "slimeballs and scumbuckets." Well, you might be right, but really, they are just salesmen/women working hard to earn a buck. They are working for a company that fosters and promotes the 'anything for a sale' attitude. Ever bought a used car from a 'cheapo lot?' You'll find much the same thing. I blame the company personally. But, nobody tortured, drugged or forced you to sign. I'm sorry this happened to you, but assess the blame where it belongs.
Finally, some comments for your letter:
These people who will read your letter see a lot of such correspondence I suspect. My suggestions parallel Theo's; keep it short, keep it simple, be direct. 1) I made a bad financial decision under pressure--a mistake. 2) I failed to terminate this agreement during rescission for lack of understanding--another mistake. 3) I will not pay any more money and continue to perpetuate this mistake. 4) Rather than incur further expenses in foreclosure etc... I offer to 'deedback' the property etc... I am fully prepared to see this process through....etc.
My point: Mistake, pressure, no money, deedback. Words like 'regret', 'lies', 'struggle', 'would like to' are wishy-washy. Personally, I don't think you'll have much success, but it's worth a shot. Maybe they'll cut you a deal to reduce your outlay and their losses.
Good luck.
Sorry if you find my words hurtful or offensive, but the truth hurts.