If one verse in the Bible defeats Calvinism, then Calvinism is untrue...and I find that at the very least, Romans 5:2 defeats Calvinism for those who are spiritually able to see what is in front of them.
How about reading Romans 5:10.... where it says that
while we yet hated God He reconciled us to
Himself. Not we reconciled ourselves to Him. Or Romans 3:24-25, where we are "justified by His grace", not by our faith. or in Hebrews, where it says the "He who has begun a good work in you will finish it", not "He will finish the good work you started in yourselves." Or John 6:35-40, where "All that the Father gives me will come," not "All that give themselves to the Father will come."
I could go on, but I think these will suffice to show that your theology is just not grounded in careful Bible study.
For the record,
this can be considered where I showed you a contradiction in your theology.
[Thought I would like to add Romans 12:3 , where it states God has allotted each a measure of faith.... but then how is it of us?]