Nikaah & Marriage Issues

Touching one's sister with lust

Q: If someone touched his own married or unmarried sister with lust, will this nullify his sister's marriage?

If she is unmarried at that time (when the incident happened), will her marriage be valid in future? What is the ruling if she is married at that time (when the incident happened), will this nullify her marriage?

Mother telling the son to never remarry

Q: If a man got married and his mum told him that he must not marry again and he's been through hell in his marriage. His mum is late now amd his kids are grown up and working. He found somebody in his life who is going through as much as him. She was an orphan and now he wants to know if he can marry this woman despite what his late mum said. He is only living in the house because of his kids. Can you advise if he can marry and be happy again?

Wife refusing to sleep with husband when he is drunk

Q: I am a revert to Islam for the past five years now so my knowledge is limited. I would just like to know if it is haram or anything the like for a wife to not sleep with her husband in the same bed since he stays out of the house over weekends and doesn't come home. I don't know what he does and who he might be with when he does not come home. Am I transgressing by not sleeping with him?

He also drinks alcohol and does not make salah sometimes. He tells me that it is haram for me to refuse to sleep in the same bed with him. I am very confused and very heart broken.