Congrats on getting it done, looks good!
My firmware has the speeds maxed out (arduino processing limitations) if you use my recommended hardware and settings. Z axis is 8.7mm/s max (maybe 9 I think I left a buffer). If you want it to go faster change that axis to 16th stepping and you can double that speed. Careful though, speed should the last thing you worry about. Bit selection, feeds and speeds, perpendicularity, axis length, material mounting, all are more important to me.
As odd as it seems to most people, end stops on a cnc are very complicated. They do not make machining easier. When you mill something, typically, you mount the material first then zero the axis to it. If you add end stops you will then have to calibrate the end stops at the beginning of every job. Yes, they are recommended for bit changes but that is a relativity advanced subject, and you will need a z axis touch plate and calibrate the offset.