Starter can not draw too much voltage, 12 V is all you got and 12V is all you can get.
It can draw too many Amps and you will notice that because it will get very hot very quickly.
The Bendix gear not retracting will be due to a build up of crud in the spiral.
Clean it, lube it lightlt and try again.
If it jambs into the bottom of the flywheel then the retaining pin/collet has worn & needs replacing.