What are my rights if I’m paid by salary but work 54 to 60 hours a week with only Sunday off?

Your employer may legally make you work 54 - 60 hours per week, 6 days per week or even 7 days per week, and does not have to give you any paid time off.
If you are salaried and exempt from overtime, they do not need to pay you any additional compensation whatsoever for any number of additional hours.
If you are salaried but not exempt from overtime, you would be paid extra for working more than 40 hours per week though all that matters is the number of hours worked weekend, holiday, etc. is irrelevant. To be exempt from overtime, you must be salaried and also meet the criteria of one or more of the tests for exemption, which can be found on the U.S. Dept. of Labor website. Go to the website, look up the tests, and compare them to your job.
If you are not exempt but salaried, then for each hour past 40 you work in a week, you must be paid an amount equal to 50% of your effective base rate. Example say you earn $52,000/year, or $1,000 per week. Using 40 hours/week, your effectively hourly base rate is $25.00 per hour. For each hour past 40, you would earn an extra $12.50. If you are owed overtime on this basis and they will not pay you, you could contact your state or federal department of labor.