Me [43 M], my wife [37 F], her illness, in love/lust with another guy

Together since about 2003, lived together since 2005, married in 2009, had a baby in 2013.
The marriage wasn't great. In fact, folks including my counselors have told me she was abusive. I'm not going to throw that label around too heavily, but I was eager to make things better. She took a stance that things weren't worth working on. She refused to address my needs when they were explained, and refused to tell me what her needs were. I was set up to fail.
The tipping point came after we moved cities for her to die. She was found with ovarian cancer during the birth of our son. She later revealed she decided that she'd wanted a divorce before we moved, but figured she wouldn't do anything about it since she was expecting to die. She started talking divorce about six months after we bought the new house.
Well, I stayed with her. I was the doting husband. I was the super-dad. I was with her every step of the cancer fight. I'll take the blame for my own role in things sliding to a ****ty point -- in hindsight, she wanted a take-charge, assertive, more typically-masculine guy who would stand up to her bossiness, not a doormat who'd go to any length in hopes that I'd earn the affection that was being withheld. Fine, I didn't realize that until too late.
So, I read her text messages and email. I was broken and wanted to see any evidence that she even said nice things about me to friends and family.
Instead I saw, going back two years, that she was "in love" and "in lust" with a trusted family friend. She told a few people about it. It wasn't a one-time admission or daydream. But I didn't get to confront her about that.
The catch is this: I found this out after she died. A day or two after she died. Days after she died on our kitchen floor while our little boy cried in his bedroom. Just her glassy eyes looking up as I did chest compressions... no goodbyes or I'm-sorry.
That was a year ago.
It's complicated my grieving. It's left me .... a little bitter. I'm not mourning a saint who was the one-and-only-forever love of my life ... I'm mourning someone I gave everything to, even as she both pushed me away, lusted after someone I knew, and demanded my continued dedication as she slid toward death.
(FWIW, I printed out the communications re: the guy and invited him over to chat. He's a good ****. I trust him and believe him. I read their interactions and he was always a gentleman. He was what I wasn't, to her, and I think much of this was her own desperate fantasy.)
For anyone with experience in complicated grief, or applicable experience -- how can I best reconcile all of this in a way that will let me move forward more smoothly? "She was a complicated person" is a decent mantra, but feels like putting a smiley-face sticker on a wound that needs heavy gauze and tape.

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tl;dr: Discovered after wife's death that she was hot for a family friend. How to process this so I can grieve forward and relieve the bitterness?


Source.

Relish in what YOU did...you stayed with a spouse who was dying, YOU took care of a dying person, YOU stayed out of a divorce and your child didn't have to go through that. YOU did nothing wrong.
She's gone, now move on with your life...take care of your kid, and find someone who loves you from who you are. Don't allow what she did to eat at you...don't give a dead person who obviously didn't care about you any power on how you live the rest of your life.

Well facts are she didn't leave you for this guy so it wasn't to much to it. Yeah she was unhappy in the marriage, but you already knew that. You chose to stay with her as you should have. Have no regrets, you loved her and did what you felt was right.