didn't say you'd get much...
Yes, Florida is an at-will state, and the maximum weekly benefit right now is $275 per week. With the stimulus, an additional $25 per week was added to each weekly check. So no matter what, this person is probably going to have to take a huge drop in income if he quits his job and IS approved for benefits. But this does not mean he cannot quit the job instead of accepting the demotion and would not be approved for the benefits, however meager they are in the state.
Even in right to work states this does not mean you can not get unemployment if fired or forced to quit under questionable circumstances. It mostly means you cannot sue your employer for wrongfully discharging you. The employer can fire you for any reason known to man, but if they had no documented valid job related reason to terminate you, you may still be approved for unemployment benefits. Each case is individual. In many states, of which Florida is one, employers are taxed based on their "experience rating" which means that usually it is to their advantage if every employee quits and does not get approved to draw unemployment as this will cause their tax rate to be increased. If an employer demotes a professional employee to a non-professional job, or cuts his wages or hours dramatically, this may very well be interpreted as trying to force a quit.
If your job is cut back so dramatically that you are working all the hours the employer has available to you, and your gross pay for the week is less than the weekly benefit you could receive if drawing unemployment, they do pay "partial" unemployment to supplement your weekly earnings. But this is usually filed by the employer for the employees, and does not usually involve just one employee being demoted for performance issues. This would just have to be dealt with as an individual situation. If the person does agree to the lesser job and tries to work at the new position and the reduced rate of pay, and then later quits because it is not enough or he finds the new job duties unacceptable, benefits will very likely not be approved because he has made a personal decision to quit at that time, not precipitated by the employer. However, if the employer fires him because he does not accept the new job, he should definitely file for benefits. Unemployment benefits are never meant to be a good income replacement program, just something to get by on till the next job.