There are some mischievous and evil things that capitalise on people's ignorance in situations such as these, particularly when they feel nobody will do some digging and get to the bottom of what's really going on. If your friend is shouting, screaming, bellowing, etc., when he's "under" I think he's either pretending (to inspire fear or respect or he's suffering from mental illness) or something nefarious is speaking through him.
I guess if he's otherwise a decent guy with good character it's difficult to accuse him of chicanery. If you're unsure as to his motivations, don't indulge him, because if someone who's faking it realises he has you by the balls when he begins shouting and screaming jakare, then it will become a form of control and manipulation on his part.
I grew up with a fraud who did this for many years. We were terrified and always walking on eggshells around this person... until the day actual shaheeds came through and put a stop to it.
initially a couple are essentially strangers so no it is not wrong to ask permission , you wouldn't want your sister to be treated as if her consent is not required would you, else where's the difference between us and the abrahamics and others? If Guru Teg Bahadur ji told his child to cultivate love for his wife do you think constituted not getting to know her as a person first? building trust and care is prior to anything else. Wives and husbands deserve respect and care, they are not belongings