@rockstar my heart aches for you, I can’t imagine how you must feel after so long together to be told that.
The one thing I can tell you is that you are in no way abusive. Abuse requires a desire to control another; you care about her and her pleasure - that’s the opposite of what abuse is!
I suggest you look up DARVO - Deny, Attack, Reverse Victim & Offender. It sounds like you are attacking yourself rignt now, don’t - you don’t need it, and you definitely don’t deserve it!
Did your wife, at any time, say no to you, only for you to bully or guilt her into sex? That’s abuse. Did she reciprocate your advances (albeit seemingly for your pleasure), or go with what you wanted just to make you happy? Then she consented. Abusers don’t care about the consent of others, they only care about what they want.
Really the slack falls on her for faking her enjoyment of sex with you. That’s also fifty years she’s wasted in which she could have been having mind-blowing sex (either with you or a different partner), had she communicated.
She obviously loves you - and you her - so it’s important not to be rushed in your decision making. How important is sex for you? Could you settle for mutual/masturbation? Could you forgive her, ever, or is this simplyunforgivable? It’s okay if this has shaken your relationship to the core right now. Take your time, be gentle and loving on yourself and know that we’ll be here for you, whatever you decide next. Good luck.