How long does your body take to replace the nutrients lost by masturbation?

No nutrients are los. No nutrients are lost by masterbation.
None are lost. Average ejaculate in a male is 5 cc or less. You do not loose any significant amount of nutrients with masturbation. For any activity it is always a good idea to stay well hydrated so drink a glass of water.
Masturbation. Depending on the vigor of your activity, some calories might be expended -- but these would be minimal, and could be quickly replaced by eating food. If you're asking about nutrients in the ejaculate itself, i agree with my colleagues that these are minimal also.