International child support / child custody

I have been gathering information for a friend of mine on what the laws and possibilities are in Canada as far as child custody and child support. I made a post in r/legaladvice and the response was a bit... blue.

https://www.reddit.com/r/legaladvice/comments/5m41h6/getting_full_custody_and_moving_to_the_us/

My question is the same for asktrp, except I know the red lens of reality might provide some more realistic information on child custody in situations with hostile mothers.