Okay, here is a thing to remember. If you quit, and you are approved for unemployment benefits, it will take ten or twelve weeks to even begin to get them started, get a decision about whether you had a valid job related reason to quit the job. That long, in the very best case scenario, where you are qualified and are approved by decision before you would begin drawing. Then, your company can appeal again and you'll have to go through another hearing, and might be denied at this point. And if you were, you'd owe back anything you had drawn previously.
And if approved, (which means you set up for a claim monetarily, which your employer may or may not be considered a covered employer, that's the first big question) you will be drawing considerably less money than you would make working, anywhere, even at the reduced rate you have been offered as a salaried employee. In your state the max right now is about $435 a week.
And, at then end of a maximum of possibly 26 weeks, which is six months, that unemployment stops. Period. NO MORE, end of sentence, there are no extensions, there will be no consideration that you have not found another job or that you really really need the unemployment. It just stops.
While you are drawing benefits, IF you have been approved to draw benefits, as a low skilled older worker, you will be required to do a whole lot of weekly job searches, supervised by the agency and required for you to continue receiving benefits. What, reasonably, in your area, do you plan to find to do to replace your old job, having worked at it for this many years and being this old?
All that considered, if you quit, your chances of being approved for benefits are not very good. You will be responsible to prove to the unemployment agency that you had a significant change to your job situation, that you did not accept it, and that you had exhausted every other reasonable means of working things out with the employer before you quit.
If they were going to cut your hours to part time with no insurance benefits, for example, that would be more likely to be considered a significant change to your job. If they suddenly decided they were going to ask you to come in and start doing their bookkeeping, that would be a significant job change.
But even if they just up and cut your pay, think long and hard about quitting because of it. Employers are allowed to make changes to their employees wages "in the best interests of the business" and it is not considered a valid reason to quit your job in most cases. For example, if business is slow, they could lower your hourly rate but continue to give you hours, or they could put you on a set amount for the week, which is what it sounds like they're trying to do, with business being good and them forced to pay you lots of overtime.
As for the age discrimination aspect of the job, are they offering this same hourly to salary change to the other people who work with them? Are you their only older employee? In order to be age discrimination, as would be determined by the EEOC, there usually has to be evidence of what they call a "pervasive pattern" of age discrimination. And have you discussed this with the employer, have you told them you feel you are being treated differently because of your age? Are you still able to perform the work to their specifications? Are you doing your job adequately? There are many factors that would be involved in a complaint against them for age discrimination, and it will take even much longer than an unemployment decision to work them through and see if you do have a case.
If you speak with the Wage and Hour division of the department of labor in your state, they will be able to tell you exactly what the criteria would be for you to be a salaried employee, and what it would involve for the employer to be exempt from paying you overtime, If you are not being paid correctly, they will come in and investigate. You have more potential for working this out with your employer, in my opinion, than you do of being approved for unemployment insurance if you quit. It's rarely a good idea to quit, and remember, once unemployment is over, it's over, and then what will you do for a job?