So, Scripture alone matters, and the early Church Fathers and their writings are to be disregarded, as well as reason and the accumulated wisdom and experience of the Church. Yet isn’t it “adding to Scripture” to contrive such a foundational doctrine and claim that it is drawn from Scripture? Indeed, the passage at issue seems better interpreted to mean not to vary Scripture than as a command that Scripture alone may be consulted. Thus sola Scriptura is not really Scriptural but more a doctrinal contrivance that expresses Protestant anticlericalism.
I see the problem. The pro-Catholic bias causes you to unconsciously add to writings to change their meaning enough to disregard them. Since you do it with Scripture then it's no biggie to it with my words as well. This bias allows one to accept whatever the RCC spoons you from whatever source and you can be sure the passages will be carefully selected for their agenda.