I understand your fears, Munchkin can be a dangerously confusing term.
And while I never experienced the internal debate that you're dealing with, I have had it pointed out to me.
I used to look at rules and their happy felecities of number crunching as material to help inspire new characters.
I never thought to myself, "I'm going to take these advantages and these handicaps so that I end with this amazingly capable stats." I always just thought I was finding ways to make really unusual but competent characters.
Long story short, I was really surprised when I discovered that I was widley thought of in our gaming circle as a tremendous Munchkin.
Eventually it all got resolved and people saw that I wasn't a munchkin just someone who liked weird that worked. I started toning down my characters by not being as upfront about their competencies and that seemed to work out fine.
The players were only tripped off when my characters' idiosyncracies were very obviously backed up by stats, in their eyes unusual behavior that translated directly into abilities meant Munchkin.
From this we developed the flip side of the Munchkin phenomena: That people will deal with people who play characters that they don't think make common sense by calling them Munchkins because that's the simplest explanation for their exoticism.
Seems to me that you have internalized what happend to me in my group, and I think you may be better off for it.
Since you are aware of this dangerously thin line between yourself and Munchkins, just be very clear with yourself on what your doing.
To some you may be splitting hairs, but if the fact that you are doing that enables you to bring more interesting characters to the table then why should they complain.