DLA is now PIP. And if you qualify for it, you still get it even if you are the MD of a FTSE 100 company and work 70 hours a week. It is intended to meet the extra costs of being disabled, which are substantial.
As to the rest, the elephant in the room is that a major chunk of the 'welfare' bill is state pensions. What is paid to the unemployed is a relatively small sliver of the total, and if it was abolished completely tomorrow it would probably not make a massive difference to tax levels.
The real issue is to deal with the unemployable. For example, getting crack heads off their habit. Teaching people who can barely read and write the basic skills to do at least a basic job. While this is desirable and I am all for it, it would not save money in the short term but add to costs. It would be a good, long term investment though. But we don't do that stuff here. See also, rehabilitating prisoners.