I'm so sorry for your loss.
I was so close to taking that step so many times. One of the factors that started my wake-up call that I needed to leave AXH was realizing one night that I'd been sitting on the edge of the tub for a Very Long Time contemplating methods and weighing factors such as how painful it might be vs. how much of a mess it'd make vs. certainty. And only once did DS creep into those musings: how likely would it be that he'd find me rather than his passed-out dad. Even that thought didn't scare me.
The thing is about being in a spot where suicide appears to be a viable option (from my experience) is that normal emotions didn't really factor into the contemplations, because I hadn't experienced any real feelings for a while. What I'd been through, what I was going through, with AXH didn't even cause emotions any more. Overwhelmed, hurting is a close description, but that implies a feeling, too. I couldn't cope anymore. I didn't know what to do. I just knew I wanted it to stop.
Had my family known, I doubt they could've done much to change my mind. It's one thing to be told: this will pass, you'll feel better, suicide is a permanent solution to temporary problems. And quite another to _believe_ it and feel hope that stuff will change. (Did I mention I wasn't feeling much of any emotions? And hope, well, hope is an emotion.)
My father attempted to kill himself years back; my younger brother, who was in college at the time, found him and got help that saved his life. We were horrified that we had no idea that he was feeling things were that hopeless. And I think that is what generated our guilt and our rounds of second-guessing and what-ifs: not knowing enough to know that Dad needed help. How could we not? We love him so. We should have known.
And now, from this side of dealing with my own suicide thoughts, I can understand a bit of why we didn't see it with Dad.
Which is all a very rambly way to let you know, well I don't really know what.... I understand a bit of how you're feeling. And I can also see how my family wouldn't have known how close I was. And if they didn't know that, they couldn't possibly have convinced me to change my mind.
Please be gentle with yourself and your grief.
Sitting with you and wishing you a measure of peace and continued strength.