He is being safe. 10 watts per 1000 and then you need 30% unused wattage so your not running on the circuit breaker at full power. So two 1000 watts per breaker is as high as I would go to be safe. Don't mess up on your electrical as the consequences are quite high. Homeowners insurance doesn't pay for negligence and that's the definition of negligence. (Overloaded breaker). If the breaker doesn't trip, the wiring can still burn.
You cant load a circuit more than 80% of its rating.. 30amp = 24amp max load. If you wired for 240volts instead of the standard 120 you can squeeze in a lot more amps. Ex/ A 30 Amp circuit wired for 120v can only handle 2,880watts max. ((30×120)×0.8) But if you wired it for 240volt, the 30amp circuit could handle 5,760watts ((30×240)×0.8) Power hungry equipment is usually wired for 240 and up for commercial
