I am not saying you test doctimrine without Scrioture. You do, assume you include Scrioture.
I am saying your doctrine does not pass the test of Scripture.
A Jehova Witness will test their doctrine and include Scrioture as well. BUT they also cannot test their doctrine against Scripture itself and pass.
Like you, Jehovah Witnesses use Scripture but trust men to tell them what those passages really mean.
It all boils down to who you pick to fill in the gaps you see in God's Word.
Jon, you're in a deep minority here with penal substitution, from what I can see.
It may be best for you to just drop it. If you can't see then you just can't see it.