Is one ablution sufficient for ritual purification from wadi and the discharge of fluid from the male organ, and for prayer, while delaying the ablution until the time of prayer after having performed istinja' from the wadi?

There are two obligatory actions concerning al-wady: istinja' (washing the private parts) and wudu' (ablution). The same applies if water enters the male organ, such as when someone instills water into his urethra and then it exits; it is impure and invalidates wudu'.

The intent behind the obligation of wudu' upon the exit of al-wady or other nawaqid (things that invalidate wudu') is that wudu' is thereby invalidated, making it obligatory to renew it for prayer.

A single wudu' is sufficient for all things that invalidate wudu'.

It is advised to be cautious of waswas (whisperings/obsessive thoughts) and to suffice with washing the outer part of the exit when performing istinja', without exaggeration or introducing water into the inside.