Here's the part about heart and mouth:
On the contrary, the word is very near you, in your mouth and in your heart, that you may follow it.
How does that tell us which instructions to keep using the process that you are advocating?
I agree! When discussing the theory of law keeping, the discussion can go round and round. I think it would be great if you would do a demonstration, pick some instructions from the law of Moses and show us how the process you're talking about works on those instructions.
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I'll give you a real life example in a different area. I had a headlight burn out on my car. In the old days, you unscrewed the headlight holder from the front of the car. It would have done me no good to say, "Take out the old headlight, and put in the new one." There were no screws to access from the front to remove the headlight like you did on my old '67 Ford or '76 Toyota
So I went on YouTube and put in the year, make, and model of my car. Then I watched someone change a headlight. Ooohhh... You open the hood and go at it from the back. And that thingy there twists off, there's no screws!
Now, I'm a fairly mechanical person. I've done tune-ups and a valve job on my old Toyota. And I've assembled a computer from scratch. But I stared and poked around at my modern car headlight and didn't see any way to change it.
In a similar way, I have stared at the passages you're talking about and tried to apply them. It doesn't work. I'm not saying the scripture doesn't work, but the process that you're talking about doesn't say keep this law and don't keep that law.
But maybe I'm wrong. How about doing a demonstration and showing us?