I am in the same situation. I think I was born INTJ, but my parents hammered an S into me. Now I am InTJ.
I seem to go along the lines of Ni-Te-Fi-Se (INTJ) more than Si-Te-Fi-Ne (ISTJ). This is a really good description. Describes in-depth the difference between the legalist ISTJ and the analyst INTJ. In my case, there is not really a balance. I phase in between them both.
Reyson: ...If you were to change your ways, I'm sure we could rebuild the relationship the two of us once shared.
Naesala: Oh no, that I could never do. You see, humans are essential to the fulfillment of my ambitions.
Reyson: You've changed, Naesala. If this is the path you've chosen, I've nothing left to say.
The problem with the idea of 'balance' between the 'second letter' for an INTJ is that that 'second letter' stands for your leading function, Ni for INTJs and Si for ISTJs. Your attitude sounds like that of someone who hasn't researched MBTI too much.
I'll give you some help. Ni (introverted intuition) and Si (introverted sensing) are very different but do have significant similarities, making an INTJ seem like an ISTJ or vice versa.
To give you the short of it, Si sees a pattern of 'what is' and internalizes it to orient one's self. Ni is trickier, but I'm pretty sure that it's like Si but instead of using the pattern to orient one's self, it manipulates the patterns and does not necessarily trust them because they can so easily be manipulative.
Ni is a lot more abstract and possibilities-oriented. Ni comes up with theories, internal models, and so on.
Si is more experience-oriented and concrete.
I think it is possible for a person to be borderline between S and N (although I'm certainly not, LOL, I'm about as high an N as they come). This borderline S/N would probably result in a strange mix of sometimes using Ni as dominant and sometimes using Si, completely changing the functional order. The difference is, one functional order is natural to the person and the other is not. The natural order would be one's 'true' type.
Out of curiosity, though, how did you come to the decision?
-I think I lack the creativity that comes with being an INTJ.
-I am a major realist.
-I cannot stand nonconformists. I mean.... seriously, what are YOU going to do to change the way things are?
-I enjoy repetition
-Organizing things by alphabet, color, size, theme etc...
-I Learn my mastering facts. Philosophy kinda pisses me off because I don't feel like anything is being accomplished.
-I can assimilate into any environment so it appears that I am extroverted,but I'm definitely not.
-And I'm good at pretty much anything I do or try. ...Even if I don't really understand it.
-However, I am more future orientated (like and INTJ) as opposed to the "here and now" like an ISTJ.
-And I don't believe in God. I despise religious institutions. ....Which goes against the ISTJ-ness "valuing tradition and religion" idea. But, at the same time, I value facts and details, so religion just does not seem very practical or reliable to me.... So maybe that is ISTJ-ish?
I don't think a person's religious beliefs have much, if anything, to do with MBTI. The reasons WHY they adopt those beliefs (or lack thereof), though, tend to correlate somewhat. So yah, your reasons for not being religious seem more S than N to me.