بسم الله الرحمن الرحيم
If nothing like madhi or semen was discharged then neither wudhu was broken nor fast. However, this act (masturbation) is an abhorrent and sinful act. It also causes lots fatal and unbearable diseases.
Note: The answer is correct. It is not valid to appoint the wife as imam for salah.
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.