"Johnny’s father, who is in a new relationship, does not pay child support despite being in full-time employment. But he looks after his son two nights a week as well as buying him shoes and clothes. Jackie feels her ex does all he can. The couple split up before Johnny was born."
Does "in a new relationship" mean newlywed?
It's not certain if it just means that he has recently started dating someone, or if he is recently married. I assume the first, but someone might use "new" to mean "new after Johnny's mother" instead of "recent."
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.