Nikaah & Marriage Issues

Q: About 7–8 years ago, when I was newly married (around 1 year of marriage), my husband suggested we do arm-wrestling for fun. With his permission, I also did arm-wrestling with his four brothers. At that time, I did not feel any lust or desire from my side at all. 

I noticed that the brothers looked a bit excited, which could have been because they had never held a woman’s hand before but now I am worried. What if they might have felt lust at that time, 1 of them asked for a re match even though I lost from all of them but I said no 1 time is enough now I cannot ask them directly as it would be very embarrassing and it was almost a decade ago. Now I do proper hijab and cover my face too. 

My question is: Does this cause hurmat-e-musaharat, and is my nikah still valid? 

I also suffer from waswas (intrusive doubts) in religious matters, so I want clarity and peace of mind.

Q: Most countries today have set the legal minimum age of marriage at 18 or higher. In light of the hadith commanding obedience to those in authority so long as it is not in disobedience to Allah, does this mean that we as Muslims are required to follow these laws regarding marriage age? What is the opinion of majority scholars?

Q: Id like to enquire, how often is the husband required to take his wife to visit her parents if they live in another city (500km away). 

Is there any requirement to the amount of days the wife should spend at her parents if it will be away from her husband?

Q: A man has more than one wife. If he travels with more than one wife, is it compulsory upon him to exercise equality in their night turns during the journey?

Q: Few months back my very close friend started to like a Hindu girl (who is married to a Hindu with 1 child). Me and 1 more common friend knew about it. We advised him to move away but this girl was separated from her husband (but still in marriage) as this guy used to drink and beat her up. She is not happy rather scared of him. On our explaining, he convinced her and she had converted to Islam. We follow hanafi fiqh and as per our knowledge her previous relationship (marriage) is finished with Islam. 

Is it okay for us to do my friend's nikah with her after completion of iddah (3 periods). Is it allowed as per Islam? There is no way she wants to go back to her husband as she is already separated. Doing divorce will cost a lot in Bhutan (her own country) and she can not afford it? Please guide us if we can do nikah for him and her.