Is there any way to test a breaker?

746watts =1hp IIRC,so 2hp is about 1500,and 1500/120=12.5Amps
The motor plate says 15, so that is a 20% safety, or My memory is poorer than I thought.
If it draws double to start, when the unloader is properly adjusted,then you would need 20/25 common breaker.
The slo-blow is a good option
But, another is to just crank down the unloader, and wait an extra bit for the pressure to come up.
Breaker-heaters do get tired after too many trips.