God would have all men to be saved and come to the knowledge of the truth....
Not just the followers of Calvin!
You are misinterpreting most of the salvation scriptures. Salvation, according to Greek interpretation, means "a deliverance".
There is "a deliverance" here in this world when a babe in Christ "comes unto a knowledge of the doctrine of Jesus Christ.
Isaiah 28: 9-10, Whom shall he teach knowledge? and whom shall he make to understand doctrine? them that are weaned from the milk, and drawn from the breast, For precept must be upon precept, precept upon precept, line upon line, line upon line, here a little, and there a little.
After we are born again, we are babes in Christ, living spiritually upon the milk of the word. We gain knowledge gradually, as we study, and hear the gospel explained by those men who God has called to preach the gospel.
This is why, in Matt 10:6, Jesus instructs his Apostles to go and preach to the lost sheep (babes in Christ) of the house of Israel.
God does not call preachers for the purpose of preaching to the unregenerate that cannot discern the things of the Spirit (1 Cor 2:14), to help them to be delivered (saved) eternally, because that is done only by the grace of God, without the help of man.
God's purpose in having his called preachers to preach to babes in Christ is so that they may be delivered (saved) from their lack of knowledge, of the righteousness of God, that is explained in the gospels.
This concept is further explained in Romans 10:1-3. Paul is praying that the babes in Christ, evidenced by the "zeal" of God that they had, of the house of Israel, might be delivered (saved) from their lack of knowledge of the gospel, and stop going about trying to establish their own righteousness, by their works.