1. Could I have done something better?
The answer honestly could be yes or no, but wondering that will not help the matter. The time for what could or couldn't be done has long past and worrying over it now will do nothing but upset you more and even led you to question the very foundation of your relationship. It isn't worth it and it isn't helpful.
2. Will I ever move on?
The answer is Yes, as long as you try!! Take time to grieve because losing the one you love hurts like hell, but refusing to accept the end will leave no room to start a new beginning. And a new beginning is exactly what you need, even if it is a new beginning of a glorious single life.
3. Was it worth this pain?
If it hurts you so much you are questioning this, then Yes, your love WAS worth that pain. Love is wonderful because it makes you feel happier then you ever thought possible, but feeling that happiness is always a gamble because with that happiness comes indescribable sadness. While the pain hurts, the happy moments will always make it worth it after the sting of the break up wears off.