I'm having a horrible time with my job in Michigan. I'm the salaried manager of a small retail store, and have worked there for three years. Over the past few months, everything started going downhill. There was a complete structural shakeup, and many changes have been made (most of which are not an improvement, from my perspective). Among other things, my work duties have changed. There was and is no written contract for my position. However, many of my job responsibilities have shifted over to my boss (who is in my store for approximately two hours per week). This includes making the store schedule. I am now being required to work alone in the store on the cash register for 35 hours per week. (I'm required to work 45 hours per week total). It is impossible for me to do my job effectively in the 10 hours per week I have left. So I have two choices - I can put in the extra hours necessary to do my job correctly (which would put me at around 60 hours per week); or I can put in my required 45 hours and leave a lot of things left undone. In the past, I have never hesitated to put in extra hours when necessary - when the store is shorthanded, when someone gets sick, holidays, etc. But this apparently is going to be a regular, every-week situation.
What are the rules regarding salaried employees and number of hours worked? If I cannot complete my duties in the 10 hours per week allowed, do I have any recourse, or should I just start planning on 60-hour workweeks until I can find another job?
*another question - if bonuses are part of the income, and the bonuses are paid much later than promised (as in over six months later than promised), and the check does not include everything it's supposed to when it's finally received (basically, only a portion of the earned bonus was paid), is there anything I can do?

I did a little more research, and from what I can find, it seems that I am not considered an exempt employee if I spend more than 40% of my working hours on non-managerial tasks. If I work on the cash register 35 hours per week and have to put in 60 hours total to complete my job duties, even assuming that I can do some managerial functions while on the register (say, 10 hours of the 35) would put me at 25 hours non-managerial and 35 hours managerial. Thus, 42% of my time would still be spent performing non-managerial tasks. (Keep in mind that during my time on the register, I would very rarely be overseeing other employees, as I would be working completely alone for the majority of the time).
In a standard 45 hour workweek, if I spent more than 18 hours doing non-management functions on a regular basis, that would classify me as non-exempt.
Is my math/logic flawed somewhere, or is this correct?

To answer your initial questions first, there are no laws in Michigan limiting the number of hours an employee can be allowed to work. If you need to put in 60 hours to complete your work, then you need to put in 60 hours.

Bonuses are, for the most part, not considered wages and can be paid pretty much as the employer wants. There are exceptions, such as when the details of the bonus distribution are established by contract, but for the most part, it's pretty much up to the employer.

With regards to your followup question, I'd take that one to the Michigan Department of Labor.