| To answer your questions, here are some of my thoughts on the issues that you have expressed a concern;
1. Can I just stop the payroll since I don't have any income coming in?
Yes, you can stop the payroll anytime you want, and now would be good time since you have no more income associated with your business.
2. How do I show this on quarterly filings to IRS?
You should report a Zero payroll for the remaining payroll tax returns that are still outstanding for the tax year. Also, do not forget to file the 3rd and 4th quarter payroll tax returns along with the "Annual FUTA 940 tax return" and the Annual W-3 returns as well.
3. I was running my payroll myself with quick books online. I still have money left in the LLC/S-corp account which I plan to pay myself as a distribution end of the year. Can I continue to run payroll at a lower salary or reduced hours since my LLC/S-corp doesn't take much of my time anymore and I don't work for client anymore?
I would simply take a distribution if this amount is not significant. If it is a nominal amount say a few thousand dollars or so, I would recommend that you take a distribution. Then I would proceed and officially dissolve the S Corporation according to the rules established in Florida. I would certainly consult a Florida tax expert to assist you in this endeavor. | 
