Man to man

Hi teachers~

I have two questions today.

Q1.

I am wondering if it's ok to say 'man to man, instead of one on one.

I was talking to a non native English teacher who lived about 10 years in the states and she said 'man to man.'

I was talking about one on one class (one teacher and one student). Dictionaries say they are different but I am not sure.

Q2. I am looking for an expression to describe a situation where two people holding hands each other are forced to let go of each other's hands.

For example, a mom and her son were walking hand in hand in a crowded place ( mall or carnival), and then they were pushed by people and had to let go of each other's hands.

I was trying to talk about a mom who lost her boy in public because she couldn't keep hold on to him, but I didn't find the right expression. It's ok if there is no expression for that. I would appreciate it if you let me know any expressions for the situation.

Thank you~~