On paper, there is little financial advantage in struggling on, as you are, as you say, in negative equity and you seem to have very little quality of life.
You really need to speak to a professional as soon as you can, please visit
www.iva.com, read the reviews etc and take time to speak to 2 or 3 different providers.
No amounts are set by the Government, but there are guidelines that IP's have to operate within. Things are never black and white, if you go BR, then without the mortgage and secured loan, but obviously with a rent instead, would you be subject to IPO's? Would you lose any vehicles?
The answer is that, without more info, I don't know, which is why you need to speak to someone as soon as you can.
Regards,