For wire sizing could i get away with 28 gauge for the everything expect for purple, yellow, green and the wires coming out of the power supply (those would be 16 or 18)?
You should add the blue from the Mosfet Source to ground to the higher current list.
I think the #28 is fine, Unless you have very long runs you can likely drop the 16 /18 to a number 20 if you wish. Otherwise 16/18 would be fine.
The 1N400x is fine (x = any of the 1N4000 series will be OK here.)
Good luck