Is it permissible to masturbate by hand when speaking to one's wife via audio and video call over the internet, knowing that masturbation is forbidden? And does this act fall under the category of enjoying one's wife or "except with their spouses"?

It is permissible for a man to enjoy speaking to and looking at his wife or her picture via chat programs, while being careful that no one else sees. As for masturbation by hand, it is fundamentally forbidden, unless one fears committing fornication, in which which case it becomes permissible. Sheikh Ibn Uthaymeen permitted spouses to talk about sex and arouse each other to the point of ejaculation without using the hand if the husband is traveling. However, using the hand is not permissible except out of fear of fornication.