Just because other people write about a couple in fanfiction still doesn't mean that it will work. People write out-of-character couple fics all the time, so it's still possible that this couple won't fully work no matter how or who writes it.
You asked if the plot is still doable. I said it might not because Proton might not want to be in a relationship even if you want him to be. That's how I answered because that's what you asked.
Instead you wanted to know about a part of his characterization, which could only be answered if you posted the story in question. While you did today, it wasn't posted yesterday, and I couldn't use it to answer your new question.
This thread isn't for characterization help. It's for plot help, which is how I answered. The only way to get an answer for your current problem is to wait for someone to read and review your story.