How can the questioner move past her emotional experience and trust in Allah's compensation after her engagement to a religious man who forbade her from permissible things like the internet, and considered her obedience to him a prerequisite to her understanding the reasons for the prohibition? And was she mistaken in anything?

There is no harm for a Muslim woman to benefit from the internet and use it for what is beneficial. A husband preventing her from it, while knowing her uprightness and good character, might be an undue harshness. Her belief in divine decree and destiny alleviates the pain of the engagement annulment, for everything that occurs does so by Allah's decree and destiny. A person may dislike something, yet it is good for them, as Allah Almighty said: ﴿And it may be that you dislike something while it is good for you, and it may be that you love something while it is evil for you. And Allah knows while you know not.﴾, and His saying: ﴿But perhaps you dislike a thing and Allah makes therein much good.﴾. Recalling these meanings of faith will alleviate what you are experiencing. Occupy yourself with obedience to Allah and supplication, and Allah will compensate you with something better than what you missed.