Am I the friend with the RC? :lol:
Hmm... That's a tough one.
I've never been in a similar situation really, Main reason is because I've disciplined myself into maintaining good road manners, Any time I catch myself acting up I stop on the side of the road and just stop, Stop everything, Relax, Breath, Calm, Think, Correct.
Sometimes you have to ask the bigger questions, Is it the bike? Is it me? Do I have a problem? How can I fix it?
I would say getting something slower wouldn't help much because it's still an issue and it's going to continue to be, You just won't notice it because you're limited.
I bought my 450r and just pounded it out on the track which helped a good amount, I know you can't really do that though which makes things tougher.
I think you just need to fight yourself and build the will and the strength to say "I need to relax" and do just that, I struggled with that quite a bit when I was a little younger, It didn't really affect my riding but there were other things like spending time with loved ones or something where my mind just wouldn't slow down and enjoy the moment.
I still have problems not living in the future but I've learned when to calm the f*** down and just take it easy, Any time I start to feel anxious like that I just change my breathing, Open my eyes and focus on what's around me, Shut everything else out but right there, Right then, The only sound you should be hearing is the bike.
So to answer, I think you could work it out and keep the k6 but the ruck would restrict you from speeding, Not necessarily a good thing if you get in a tight situation because now you have no "Get out" power.
You should ride that dudes ninja 250 real soon though and see how you feel afterwards.