Stepson touches stepmother with lust and touches other females related to him

Assalaamualaikum.
Does hurumat musahara take place in the ffg. & whose Nikah will break:

1) If a son touches his father’s wife with lust? i.e his step-mother.and vice-versa she responded to his advance or she made the advance? If the Nikah breaks then what happens if the father died and he wasn’t aware? How can a person compensate for this? Will the father be punished? Will a person’s repentance be accepted if he did this? Will the inheritance have to be re-distributed and will the step-mother and the son receive any inheritance? Can the step-mother still stay with the father’s other son who looks after her and sees to her needs?

2)If he touches his own mother or even saw his mother but he was 10 or 11 years old and experienced erection?

3)If he touches his mother’s sister?

4)If the boy looked at his mother in law but not her genitals? Her body part from above the breast to below the knee maybe her calf (below the knee) or face or hair or hand etc? He never touch her however.

A Mufti replied it will not break in question 1) but in Behisti Zewar and other Q&A like Mufti of Sherwood Darul Ifta I read will break. I changed my life and wasn’t aware of the Masala. Please help as I was guilty of this sin. I repented sincerely.Will Allah forgive me and will my dad have died a Muslim but be punished because of me? He died a normal death however. Will I die a Muslim because I maybe a cause of zina for my dad till he died if his Nikah broke? I don’t want to be punished. I want Allah to forgive me. I am really remorseful and never went back to this sin.
Jazakallah Khair