Filling the gap in the saff if the muqtadi leaves during salaah

Q: There is a rule in Bahishti Zewar that it is makrooh to stand alone in a row. The person should pull a person back from the row before him. What happens to the gap formed by the exiting of the said muqtadi to fill the previous row?

If a Muqtadis wudhu breaks during prayer, should he just leave and leave a gap in the saff? What should he do in this regard?

Child born out of wedlock

Q: If a child is born out of wedlock (through zina), will he be attributed to the mother or the biological father? The biological father is pleased to take him as his own child and give him his surname. Is he the responsibility of the biological father and will the biological father have any rights over him? What is the shar'ee ruling in regard to a child born out of wedlock?

Throwing food at the groom before the wedding

Q: When people in my family get married, they normally make a big thing with the groom. They splash him and throw food on him and make a big noise. This is before the nikaah. When he gets married then they trouble the couple and on the first night they peep and other things.

Would this be emulating kuffaar? I hate participating in this, but they force me to and get angry when I don’t participate and really give it to me. How should I combat this?