[xzins]

2 Timothy 3:16 the reference is to the Old Testament if you take it literally.

Not so.

Peter himself called Paul's writings "scripture."

Jesus Himself said that others would find Him through the testimony of the Apostles.

There is no denying the immediate level of inspiration that accompanied the writings, dictations, and authorizations of these Apostles.

[annalex]

Peter himself called Paul's writings "scripture."

I personally dislike the argument that 2 Timothy 3:16 does not apply to the New Testament, for these reasons you cite. Nevertheless if one takes 2 Timothy literally, this is what it refers to the Old Testament, inclusive of the Deuterocanon.