I conducted some research and eventually decided to implement a planetary gear system to reduce the input RPM for gear testing, as it provides greater strength. I also designed a gear clamp system which allows me to clamp the gears onto the drive shaft reliably with a hex keyway. Below are a few screenshots of the hex keyway system and of the planetary gear system. I am going to conduct a preliminary test print to make sure the gears mesh well, they should mesh fine as my assembly indicates but the tolerances may not work out, or the gears may be too weak, etc.