That is why my answer to your sixth question is an unqualified "No." The St. Lawrence seaway would take eight or more years to build.
"Epistles-from-Pap-Letters-from-the-man-known-as-The-Will-Rogers-of-Indiana"
Durham, Andrew Everett
The Inlet ends there, the seaway barred by these frowning declivities.
"The Hidden Places"
Bertrand W. Sinclair
Thus the discovery of a strait, or the cutting of a canal, at the Isthmus of Panama would at that time have opened to Europeans a shorter seaway to the Orient.
"The Panama Canal and its Makers"
Vaughan Cornish