Child using adult account/time limits

No you cannot set limits on a parent account as it is an adult account. you cannot change an adult account to a child account either. Any limit you set will have to be a physical limit you cannot use anything software wise since they are an adult.

Always recommend starting a child off as a child account.

This is interesting put this on your account should work , https://news.microsoft.com/en-gb/20...t-the-time-their-kids-spend-on-specific-apps/

Typically changing the account alias would be the best way to remedy this situation by just flip-flopping which account gets who's email. Follow through this support link to make sure you're doing it correctly, its normally a pretty straightforward yet frustrating
process.

https://beta.support.xbox.com/help/...nt/change-email-sign-in-for-microsoft-account

If you like to reset screen times again, support has you covered on the proper way for that too.

https://beta.support.xbox.com/help/family-online-safety/online-safety/set-screen-time-limits

If I'd recommend it though, a usually hassle free method of sharing content between accounts would be by setting the Xbox as the Home Xbox on the primary account used. More details on that here.

https://beta.support.xbox.com/help/hardware-network/console/my-home-xbox

...I set up a child account and all the limits etc. Everything was going as expected then I realised it wasn't anymore - he had somehow switched back to using my account. ...

Accounts don't "switch back" by themselves. Your kid probably knowingly used your adult account instead of his own account, because he knew his child account is being restricted.

Also, the purchased Xbox items are not connected to the email itself, but the Gamertag connected to the email. Unfortunately, you can't transfer the Gamertag to a different email, which technically ties the purchases to the email as well.

Even if you managed to get your kid's email as an alias to that Gamertag with purchases, it would still be an adult account that can't be restricted.

Your only options really are: Let your kid play with the adult account to keep his virtual gifts and be unable to restrict his play time, or if play time restriction is more important for you, set
up a Passkey on your adult account to prevent your kid from playing on your adult account and forcing him to use his child account.

Be aware that your kid could try to create a new (adult) account to circumvent the restrictions again. To prevent that, go into settings and System settings. In there you can select "Control Offline Content". In that setting you can un-check "Let people
download and make new accounts" and also set the age level for access when no one is signed in and create PassKey to prevent changing those settings

If it helps: The Skins/Gliders/Backpacks are purely cosmetical and don't change anything in the game but the appearance. Your kid doesn't get any (dis-)advantages with these skins.

As for losing his XP: See it as a way to "punish" him for (ab-)using your adult account.

Try to explain the situation to your kid like this:

Your kid redeemed the Skins/Gliders etc. on your account, basically "gifting" you the stuff you gifted him. Thank him for those nice gliders and the XP boost he gave you, and make him play on his own account again.

I know you have said your not techy, but in this type of situation it might be best to set time limits up through your router. Some routers have apps for your phone that make it easier to set up. Not sure if you have ever accessed your router before.