Apple Family Sharing Problems

My family has recently attempted to set up family sharing on our iPhones, but we're having a few problems.

Previously each family member was logged into their phone with their own iCloud account, but under the iTunes & App Store setting logged in with my account. That allowed us to share purchased music and apps, but have separate iMessages and calendars.

We wanted to switch to family sharing, but have run into a few problems. I'm leery of making random changes due to the constant threat that some changes can only be made every 90 days. I'm hoping some here can provide their experience.

1) My daughter's phone is logged in to her iCloud account. Under Family Sharing it says that she's using her account to share purchases with the family. However, the apps on her phone will not update, but rather prompt her for the password to my Apple ID, even though the iTunes & App Store on her phone is logged into her Apple ID.

2) My son's phone is logged into his iCloud account. However, under Family Sharing it says that he's using my account to share purchases with the family. Don't know why it says that since we added him to the family group the same way we did my daughter, but I'm threatened that I can only make a change every 90 days if I change that.

3) My son wants to subscribe to an individual Apple Music plan. (We're not big music listeners--odd I know--so we don't want the family plan.) When he attempts to subscribe he gets a warning that his device is linked to another Apple ID and he needs to change his Apple ID in order to subscribe, but again threatened that he can only change that every 90 days.

Does anyone have experience with these situations that could offer some guidance?

Basically, I want to end up with Family Sharing where no one is prompted for my Apple ID password and that my son can subscribe individually to Apple Music.