Nice Job! A good understanding of mechanics and electronics goes a long way to make a successful rebuild.
Over the years, I have R&R several starters. (Remove and Rebuild) - small gas engines, bulldozer, marine engine, snowmobile....etc (even my Kubota)
I have found that the older starters were DESIGNED to be rebuilt. The copper contactors are intended to be 'flipped over' to reveal fresh copper surfaces for many more years of life. Often just a handful of basic tools is all that is needed to get a starter going again. (A bulldozer which fails to start in the middle of the forest is NOT easy to take to a shop)