I understand what you believe SS is. As the article above states "Scripture alone is authoritative for the faith and practice of the Christian". I take that to mean that the bible alone is able to teach the Christian the TRUTHS about God. But this does not seem to be happening when we see sincere God fearing Christians disagreeing on what the bible teaches.
Do you see the problem?
Let's look at this objectively without bringing in anything the Catholics do. SS should be able to stand on it's on, it should not need the fact that you think Catholicism is wrong to justify the truth of this praxis.
For the purpose of this discourse, let's even state that the Catholics are wrong in their doctrines. Would that automatically mean that SS is right? No, it does not. If SS is true, then it must be shown to be true on its own accord.
From reading all the verses in support of the praxis, it can look like that is exactly what the bible is claiming; however, the true test must be that it accomplishes what it claims it can accomplish. - i.e. Scripture alone is authoritative for the faith and practice of the Christian; but not just individual Christians reaching different subjective conclusions, but as a whole body of Christ.
I don't see it working. Do you?