Why two breakers (one for the line, one for the neutral) on a single-phase line?
What you have is a 240V breaker and circuit. The white is NOT a neutral, but being used as another hot...which is perfectly fine and legal. Newer codes require such a white to be re-marked as a hot.

DO NOT replace ANY breaker with one that is larger. 99.9% of the time the wiring is appropriate for the breaker feeding it. Installing a larger breaker could create a fire hazard.