Yep, confusion about DLA.
DLA is not intended to be an income or liveable - it's to contribute to the additional cost of specific mobility and personal care needs (so David Blunkett is eligible for DLA because being blind he would need some assistance with housework). You don't get it for "being disabled", you have to have specific needs.
The income-replacement benefit, that people unable to work because of disability have to live on, is ESA (formerly Incapacity Benefit).
That varies from £56.25 a week to £105.05 a week (very few get the top amount).
And yes, unlike the MPs' £160 for groceries on top of their salaries, that has to pay for groceries, bills, clothes, bus fares, etc, just like someone on JobSeekers. And for the many people not well enough to work, but not "correctly" disabled for DLA, it has to stretch to all the disability extras as well - heating on during the day, buying a food processor because you can't slice and mash, paying for delivery and missing the marked down stuff because you can't easily shop.