How( martial artist only ) slow should i practice each movement ?

Practicing slowly allows you to make sure you have the proper technique. It also helps with muscle control. Practice as slow as you need to to ensure you have the correct posture and alignment. You can then speed up gradually, going only as fast as you can while maintaining good form. Speed and power come much more easily when you have good technique and control. It sounds like your practice is working for you, and ultimately you should do what works for you and what you feel comfortable with.