You are doing a great job thinking through everything and processing. All of your feelings and emotions are SO normal. I agonized and prepared and prayed over the decision for almost 2 years before we actually started proceedings. It took another 3 years to complete the divorce after that. So it is a journey. I went back and forth so many times wondering "is this the right thing? Did I do everything I could?" It sounds like you are doing the same and that is great because you clearly are not taking the situation lightly and you are definitely considering your children's needs first and foremost, so you are definitely handling this well.
Just know you are not alone and keep reaching out and looking for your answers for "if" you may need to be divorced and if so, "when" might be the right time. Like Rainy Day, I am SO much more content and peaceful not being in my marriage and although it took a great deal of time, when I knew it was the right decision, I had so much peace about it. That's not to say it was easy. Making the decision truly just begins another "phase" of a usually challenging process. Starting that process knowing you have done everything you can will surely help and you are clearly seeking that. Good for you!
I absolutely LOVE your cake and crumb analogy!
Best of luck and please keep us posted.