What's going on when you say it's not running properly, is it slow, crashing, flashing, etc? Have you gone through the other suggestions made in here: https://care.king.com/en/candy-crush-saga/cant-get-your-games-to-load-on-facebook-check-this-out
If you've been logging into two different accounts, try this out: go into Safari and make sure you are logged into your FB account from the FB site directly. If you've already done that, clear cache from Safari and try again. When you hit connect in the game it should sign you into that account.
Have a go at the suggestions given in the thread below, you've not said what OS you have so put linked both iOS and Android for you. Hope it helps: https://care.king.com/en/candy-crush-saga/lost-your-connection-to-facebook-ios https://care.king.com/en/candy-crush-saga/lost-your-connection-to-facebook-android
Have a go at going through the steps suggested in the threads below. You didn't say which OS you have so have put both iOS and Android for you, hope it helps: https://care.king.com/en/candy-crush-saga/loading-crashing-issues-ios https://care.king.com/en/candy-crush-saga/loading-crashing-issues-android
Strange you're also having the forbidden error, blocking access to their own games intentionally wouldn't be a smart move. Did the error message contain anymore information or did it literally just say "Forbidden"?
What's happening exactly when you're trying to connect to Facebook, are you getting an error message? Having a Kingdom account shouldn't effect it, I've got both and they work fine, you just can't connect to both at the same time.