They'd **** him up tbh. Worse for being white too, can't have their precious good Muslim son being poisoned by evil western values. What a joke
God forbid, if he was my son.... This is what I think I would do: I would first advice him to take a U-turn immediately by repenting and cutting himself off from partying,dating etc.
If he doesn't do it immediately I will semi-disown him i.e will only contact him to give him advice to come back to the straight path. And once he changes his ways and sincerly repents I will consider him my son again and try to treat him normally.
But most families imo would straight up disown and cut all ties and thats what he should expect.
Can't really say, it all depends on the parents and how hardcore they are and how close they are to their child
speaking as a south asian though i tend to find that a lot of strict south asian parents won't disown if its their son. daughter most likely but son very unlikely. they will still try to break it up though, whatever means possible. first putting heavy pressure on their son then treating the would-be daughter in law or her family badly. if the marriage still goes ahead they might just keep it quiet. thats how it was for one of my cousins anyways, everyone knows he is married but his parents still tell everyone he is single.