How can the Sunnah of the two Rak'ahs on the wedding night be performed with continuous emission of pre-seminal fluid (madhy) just from speaking with the wife, let alone meeting her?

If you can control your desire until you pray two rak'ahs with your wife, that is good. If madhy (pre-seminal fluid) is discharged and you want to pray, you must purify your body and clothes from it, then perform ablution (wudu') and pray. However, if the discharge of madhy overwhelms you and you cannot stop it due to surging desire, then prayer is not valid in this state, and you bear no sin for not praying these two rak'ahs. Be diligent in observing other Sunnahs, and do not pray while in this state, as you are not afflicted with سلس (incontinence).