No. The offer is real. And I think the Calvinistic descriptions of how this works is far better than what I see from the free will side. It does not appear to me that after Christ accomplished redemption on the cross that God said "Now look. I have provided all the tools you need for salvation and you're going to have to use them or be lost." It does not appear to be a matter of God votes for you, Satan votes against you and you cast the deciding vote, either. If you can get away from the TULIP for a moment, which is not what Calvinism is all about, what you have is an unfolding plan where the gospel is preached, some come and are saved and an allowance is made for the fact that God was in charge and knew what He was doing all the while. Even in your example above of Jeremiah 29:13 notice in context what you have is a prediction where God is completely in control. Look at verse 12. God is not having to wait and hope that they might make wise use of their time in captivity. He knows exactly what they are going to do and exactly when.
Jonathan Edwards specifically preached that way. Surprisingly so did Owen. In fact we had an argument on here a few months back where I pointed out that every one of the Puritan preachers used the "Behold I stand at the door and knock" as an invitation even though most modern Calvinists criticize that. I have a sermon from George Whitfield where he tells people to go home and pray a prayer that basically asks Jesus into your heart. Then you have Spurgeon, Andrew Fuller, the group called the Marrow Men. Most recently I have been reading a guy named Sam Waldron, who has a book out called "The Crux of the Free Offer of the Gospel". I admit that logically some of the tenets of Calvinism are hard to reconcile. But I maintain they are no worse than other systems. You don't really have to go there to be a Christian but if you do it is not easy to reconcile the various scriptures along with our human point of view - in that we are stuck in time, cannot see the future, and the past is only a fading memory. Plus we have a hard time knowing ourselves, understanding why we do what we do and so, all in all, I find what we call Calvinism to answer these things better than the other systems. Mainly, I like the preaching of what we call Calvinists better than the preaching of most of the non-Calvinists that I have heard so far.