What is the ruling on a mother financially assisting her addicted son, knowing that she fears harming him if she doesn't? And is it permissible for her to report him to the police in a non-Muslim country despite her fear for him from them?

There is no sin upon the mother if she gives her son money fearing his harm, provided that she predominantly believes a significant harm will occur. It is permissible to report him to the police in non-Muslim lands if that will mitigate his evil or help him abandon addiction, provided that no greater harm results from it, such as his being tempted away from his religion.