Yes those jobs exist but you need to work for a major fire alarm installer or for the fire alarm manufacture. In my company, they are called Application Specialist (entry-level which is what you should look for) then moving to Application Engineer or Systems Engineer. These positions require a electronic or electrical engineering degree. They split their time in the field and back in the office. You can specialize in certain product lines (we have a E3 Series expert) or installation (we have a fire alarm programming expert).
Pay in a entry level (this is you) will start in the mid $40k then grow to $80k after 10 years of experience. If you love your career, pay shouldn’t be a factor.
These positions are ALWAYS in demand as fire alarm systems get more complicated and bring in new technologies (fiber optics, IP, computer workstations, etc)