GG,
I agree with you concerning God's revelation of Himself in creation, according to Rom 1:19-20 (NIV), which states:
since what may be known about God is plain to them, because God has made it plain to them. 20 For since the creation of the world God’s invisible qualities – his eternal power and divine nature – have been clearly seen, being understood from what has been made, so that people are without excuse.
So not one person in the universe throughout human history will be able to state they didn't know God existed. They 'are without excuse' when they stand before God for judgment.
However, this understanding of the existence of God is not salvific. We cannot find salvation in nature without the revelation through Scripture and Christ.
We also know that God reveals Himself to all people through their consciences:
(Indeed, when Gentiles, who do not have the law, do by nature things required by the law, they are a law for themselves, even though they do not have the law. 15 They show that the requirements of the law are written on their hearts, their consciences also bearing witness, and their thoughts sometimes accusing them and at other times even defending them.) 16 This will take place on the day when God judges people’s secrets through Jesus Christ, as my gospel declares (Rom 2:14-16 NIV).
Back to the OP: 'The latest on Calvin'. The latest on John Calvin is the old Calvin, found in his writings and especially in his systematic theology,
The Institutes of the Christian Religion. I'm in the midst of researching an article: 'Did John Calvin support TULIP?' Even though TULIP was formulated at the Synod of Dort (1618-1619) and Calvin lived from 1509-1564, if Calvin were alive at Dort would he have supported its TULIP theology - based on his own writings?
The evidence I'm finding is, yes, although he sometimes puts limited atonement into similar but different language.
Oz