According to, Leave Family Sharing - Apple Support, “Any content that your family shared with you isn't automatically removed from your device. You can purchase it again or remove it”. In a perfect world when you leave the family or your mom removes you, a notification will pop up & you can do everything from your device. However, I would start an individual subscription before you leave your mom’s family. That way there is no gap of time. The 1st thing you lose are your downloads when you lose Apple Music. So if you leave the family, the subscription is lost & so are the downloads. Once you have your individual plan, then you go through settings, change your plan & organize the family for you & your husband.
I hope this helps.
Subscribe to Apple Music on iPhone - Apple Support
Share Apple and App Store subscriptions with family members on iPhone - Apple Support