No, you are not being ridiculous! It sounds like you are being taken advantage of. Your employer has placed you in an “unofficial” supervisor role, and not compensating you accordingly. Great for them, not so much for you. Even though it wasn't guaranteed, and your quota increased, the bonus was a reasonable increase at the time. I know it can be frustrating to see others making more than you. That’s one of the perils of working for a company several years - you stay on the low end of the pay scale while newer employees are hired in at a higher rate. I find that irritating as hell.
You know the dynamics of the relationships involved, but here’s what I suggest. You asked for a raise before, and you succeeded. Do ask for a raise, but don't give your notice unless you are prepared to leave. Think about how you approached the last situation, and use what worked and see if any of these ideas may help.
Tell your boss you want to find out what kind of pay increases you can expect this year. Say you appreciate the bonus two years ago, but your hourly pay does not reflect your responsibilities. State that you have taken on a lot of responsibility and need an increase. Research how much people in your kind of work make in your area. Go to Glassdoor to get salary information, or Salary.com.
Try to build a good business reason for why it’s in the company’s best interest to keep you. Consider this:
Do they need a supervisor? If so, propose that they add a new role. Are there problems because there isn't an official supervisor? If so, be ready to point those out and why it's important that you move up.
Have examples of how you help the company reduce expenses and increase efficiencies.
Have data to support how your supervision reduces turnover (that’s worth a lot right there).
If a promotion isn't possible, at a minimum ask for increased hourly pay to be equal to or higher than the temps. If answer is no, be prepared to ask for other things that are important to you:
Ask for a higher bonus, or a supplemental quarterly one.
Because your role changed, ask for a title change. Even if they don’t increase your pay, that will at least look good on your resume.
Ask for more vacation time or other benefits
If all you get is No, No, and No, ask when you can expect an increase. If it's not anytime soon, you start your job search and make a plan to exit on good terms. It sounds like you shoulder a lot of responsibility and have a great work ethic. Any company will be lucky to have you. And, all the prep you do to show your value to your current employer will be fabulous when you’re updating your resume.