Have you reported the 'blind' person for fraudulent claiming? I think there is a moral obligation there.
Yes, back pain can be awful - i suffer from degenerative disc disease, have no disc between L4/5, suffer severe stiffness, discomfort, pain and have had to give up an awful lot of my lifestyle. but (as i'm sure you have) you adjust your life as much as possible to accommodate this. You say that your pain ranges form discomfort to excruciating - during periods of discomfort is there anyting to stop you from working? (I don't want that to sound too harsh) As Fionn2011 says, there are many different jobs out there, it seems what they are suggesting you find somethign suitable for your particular condition. A non-physical job should be considered, and a lot of employers are sympathetic when it comes to illness. If you are good at the job then it shouldn't stop you being employed. Have you considered office-based jobs? Call centres etc. Perhaps they suit?