I guess I was unclear about what you meant when you mentioned your dividing line as being torah shebicsav. So tefillin were passed down; is the requirement to don them each day, the laws about minute changes in the letters that make them invalid, and the hundreds of other laws traditionally associated with them also part of the Torah shebicsav definition? If shechita was passed down (the Torah mentions it but doesn’t define it) , what about the things that invalidate a shechita or the 24 ailments that make an animal treif? Actually there doesn’t really seem to be all that much in the Torah that doesn’t rely on a communal tradition in its most basic interpretation (except perhaps an eye for an eye if one would take that literally and perhaps a few other such ideas which I can see as being pretty self explanatory )-even circumcision, to which the oral tradition assigns hundreds of details, yet which is spelled out pretty clearly in torah shebicsav with just a few requirements- yet the Torah doesn’t quite tell you where the procedure is anatomically-. To give a better idea of how you define yourself perhaps you could clarify it a bit more. Where is the dividing line that would have you consider something to be relegated to torah shebaal peh?
I don't think a dividing line exists that can clearly summarize what I do believe in and what I don't. Or maybe I haven't figured it out. That being said I'll go through your examples and explain each one.
Tefilin being worn everyday? Yes I think it's quite obvious from the Torah alone (without any tradition) that tefilin was supposed to be worn everyday and also all day. The reason why I think so is because the Torah says you should wear it without explaining how long. So my first thought is, since it's a mitzvah that is supposed to be a reminder for something. Most probably it's supposed to be a good reminder, which means being worn all the time. (Does that mean I can't ever take it off? I don't believe so, but that's a different question).
Minor changes in the letters make it invalid? Again I don't think you have to come onto an oral tradition for this. No matter how small the changes in the letters are, it's not the letter. Therefore it's not tefillin. I don't know what you mean by "minor changes" (I'm assuming you mean the crowns on top of certain letters) but regardless I think that my answer would answer that also. It happens to be that I'm not sure if the crowns are included in the letter. But however I would decide, then the above applies.
The hundreds of other laws regarding tefilin? Most probably most of them I don't believe in. But I would have to go through each thing. So I don't know.
Shechita. Things that pasul the shechita. I don't know much about shechita (neither have I thought about it much regarding what's acceptable or not according to my own beliefs) but I do know that a knife that isn't perfectly smooth isn't good. Or if you shecht too much/little it's not either good according to halacha. So that would have to be a part of an oral tradition that I don't necessarily believe in. But I do believe that the only acceptable way to shecht something is using a cutting instrument by the neck. Why do I believe that? Because that's how everyone explains what a korban is and everywhere in Tanach matches that description. Why don't I believe that having a perfectly smooth knife is necessary. Because to me a perfectly smooth knife and a knife that's a tiny bit imperfect does the same thing. So I find it not probable to say that one is good while the other isn't.
24 ailments. Once again, I haven't thought very well about the requirements of shechita according to my own beliefs. I think the word treifah in the Torah means an animal that is on the brink of dying due to another animal mauling it. So that would logically include any other case that is similar. Meaning an animal that will be dying very shortly. So I do agree with the idea of certain illnesses making an animal into the status of a treifah but I don't know if I would include all the cases that halachah says are included.
Circumcision. I don't know all the halachos either. I most probably don't believe in all but I can't say for sure since I don't know. The location of the bris I have no doubt in my mind is the right one. First of all from the fact that it's in that location, is proof that it's right. No one would decide it's there without being 100% sure. And the Arabs also believe it's there so that is also something. Why isn't it stated clearly in the Torah where? I don't know. Maybe for tznius reasons. Or maybe the primary usage of the word "orlah" in those days was used to refer to that area. So maybe it does say it clearly.
And what is included in the bris? I would imagine that Hashem wouldn't want to do any damage that affects function. So that would mean the part that has little use and is considered extra.
So did that help you understand how I understand the Torah and how I define myself? (I feel like I'm going a little off topic)
