It is impossible to tell a Calvinist that he is wrong using sola scriptura because Calvinism is all a theological speculation. You look at about 5% of the scripture and ignore or spin away the rest. There is less of Calvinism in the Bible than of fish-on-Friday disciplines.
The point remains that all these sundry Protestants say exactly what you say, that they found their strange beliefs in the Bible somewhere. No one forced them to have them; they surely do not have any apostolic tradition. They read the Good Book, that's all. Just like Calvin did.
I'll compare the Westminster Confession or London Baptist Confession of faith against anything you may wish to provide. I've been on that side before and I've seen no concise systematic theology from your side of the aisle-Catholic or (most) Protestants.
People chide Calvinists for seeming to have an answer for everything. You're the exception but you make the mistake of lumping Calvinists in with Protestants who really are more akin to Catholics in belief. Many Protestants here on this board will readily tell you they are definitely NOT Calvinists.
If you promise not to tell my other Calvinist brothers, I'll tell you the secret to Calvinists' "wisdom". If the truth be known, the only answer Calvinists really have is that God is sovereign, has ONE perfect plan and will do precisely what He pleases to see that perfect plan through. That's the WHOLE Calvinist message and how we believe the Bible to be written. Now that I've spilled the beans I'll probably be drummed out of the GRPL. However, I'm confident many will continue to say, "Yes, but...." so our evangelistic efforts will continue. :O)