What reason does your handyman give for needing a second fan in your attic? What's going to be different for your house? I'm assuming your attic is a typical uninsulated attic in the US. I live in Texas, and as far as the eye can see there are houses with uninsulated, passively-ventilated attics. Almost no one has powered attic ventilation. I have a thick layer of blown-in insulation up there, and with the volume of air your handyman wants to move, I'd be concerned the insulation would move with it.

In an ideal world, all our attics would be inside the insulated envelope of our homes, but our building standards are not there. So where you can affect energy efficiency is in improving the impermeability of your insulation as it currently exists. If you're going for energy efficiency, slightly lowering the ambient temperature of your attic in the summer heat is just not an effective solution. Spend that money instead on fully sealing all the holes around joints and fixtures that are currently leaking air between your living space ceiling and your attic, and improving the R value of your attic insulation.

I don't know if what I'm talking about applies to your house, but if so, check out this Matt Risinger video for a lot more detail.

I thought ridge vents were all the rage these days. I installed ridge vents and then put up Reflectix Reflective Roll Insulation from the soffits up to 12-18 inches from the ridge. It reduced the heat in the attic by a noticeable amount and wasn't too expensive or difficult to install. I also blew in additional insulation. I plan on adding additional venting in the soffits in the future. My experience is that fans fail, require maintenance, use energy, and tend to only cool the attic off in certain areas if not well planned out with supporting architecture and venting.

3000CFM is probably too much. Your exhaust needs to match your soffit intake in terms of how much air they move. You can't just exhaust air without replacing that air. Find a roofing contractor and not a handy man. If you're forcing 3000CFM out and your soffit vents combined allow for 1000CFM, there are still 2000CFM that need to come from somewhere and it could start coming from your conditioned space through air leaks from things like light fixtures and drywall gaps.

It sounds like you're wanting to vent the attic to cool the house? If so, insulation is your best bet. Yes it may also prevent you from gaining heat in the winter from the sun, but it will also keep the heat from your HVAC inside which is way more efficient than relying on an insignificant amount of heat from a winter sun. We recently increased our insulation to R50 and it has helped lower our bills and equal out the temperature of the house

Depends on the cfm (cubic feet per minute) of the fan. This will tell you how much it's working to replace the air in your house.

Also depends on your current circuit, and your circuit current, lol. I'm willing to bet that the current circuit is 20amp, so I don't know why he's trying to replace that. I'm willing to bet the fan is also using almost all of the available circuit. You need to find out what the draw is on the fan for that. A 20amp circuit can handle 2400 watts. But due to code limiting draw at 70%, you can only put 1680w on there legally. That's for saftey(fire) reasons.