This circuit is intended to use a 1-10Hz PWM signal as input and produce a 1-10kHz 10A PWM output. It will be used for controlling the speed of a water pump: GP1352 The PCB will be ordered with (only) SMB components pre-assembled and will be potted once the SW has been commissioned. Thus keeping the heat low is important. I can only order the PCB with 1oz copper so heat from the traces is a concern as well. Therefore I am using 4 MOSFET's even though 1 should be able to power the pump alone. This way I plan to spread the heat generation out across the board to avoid hot spots. (The potting will be as thin as possible to allow the greatest heat transfer) The desire for low heat goes hand in hand with driving the pump to its full capacity as well.
I could explain the calculations and data sheet lookups I've used to arrive at this design, but the question would get very long and I think my intentions are clear from the description and the schematic. If anything was unclear I will elaborate in the comments.
So, how can I modify this circuit to better achieve my goal?
PS: This is my first electronic circuit design. Apologies in advance for the newbness, I'm doing my best.
Schematic updated 20191001 based on input from Brian Drummond and The Photon.