I have a peerless gas boiler (PF-80). What thermostat is compatible? Currently using a honeywell CT3300 I want to replace. Also, this boiler has a display but nothing is displaying. Anyone know why?

Find a stat that has similar specs. Here's the manual: https://customer.honeywell.com/resources/techlit/TechLitDocuments/69-0000s/69-1634.pdf

Typically control stats will simply provide a contact closure to the boiler enable.

In my experience, the boiler should always maintain a specific water temp and your forced air system should be the thing activated by the stat, unless you're using radiation.

As for the display, try touching a button to light up the controller.