Good post. I wish you strength in your tough times.
I've been into and out of a flatline before. Flatlining sucks. The disgust of feeling empty. The rage at the time, opportunity, and joy wasted, never to be reclaimed. The oddness of that rage not burning within.
Check out The Power of Habit, it can help us make nofap more automatic.
One thing that helped me with the flatline was to explicitly make the rule that "testing to see if I'm capable of breaking out" would count as breaking my commitment. Saying it out loud really helped me stop trying to rationalize it.
Another thing that has helped is using chains.cc and focusing on building up a good habit by doing something active. I'm focusing on reading more books and studying a foreign language. I've found this sense of active purposes, as opposed to the asceticism of only abstaining, helps my nofap progress, makes me a better man, and makes me a happier man.