Time to bring out the halfway legal-speech here.
The EULA usually is a Agreement that you sign, therefore it is legally binding, however as with most legal documents, there is usually not a clear-cut way of whats forbidden and what isnt. For example, if you buy a Product which has a EULA, which is generally the case, you may not copy it to be sold, you may not make it publicly available. In essence, you can sell your Copy, but you cant make multiple copies and either sell them or give them away, thats a breach of said contract.
However you are within your Rights to make backup copies of any software you purchased for your own personal use, meaning im legally allowed to say make 20 copies of the game i just bought. However im not allowed to remove the DRM on it or change anything in the code that would provide me to get around said limitations. However i can, provided i have the knowledge and tools, modify the game to my liking provided it does not change the Game in any way as to make it into something else. For example, you cant mod Half Life 2 to be Mass Effect 3, well you can, but its a breach of contract. You can however modify Half Life 2 to be Half Life 2+Mods, or ME3 to be ME3 with small additions.
In short, you are allowed to change anything within the game as long as its not essentially a total conversion without prior consent from all parties involved. So you can change the FoV and such in ME3, however it would have to lock you out of Multiplayer since it might be a unfair advantage to other Players. Origin however should not have the Power to ban all of your Games and Account from its service, meaning one infraction in a single game should not equal losing all games you own.