Phizzy,
Jeremiah said the land would be 'desolate, without inhabitant' (Jer. 9:11). He NEVER said that it would be that way for 70 years. He specifically attributed the 70 years with the nations' servitude to Babylon. It's primarily the text in 2 Chron. 36:20-21 that prompted Russell's misunderstanding.
(We also know from archaeology and Ezek. 33:21, 23, 27, 28 that there were inhabitants, not only after Jerusalem's destruction, but after Gedaliah's assassination and a bunch of Jews ran off to Egypt.)
Barbour mistakenly believed that 'Ptolemy's Canon' indicated the year 536 BCE for Cyrus' 1st year. It was actually 538/7 BCE.
And as you say, 1799 was NOT the beginning of the 'last days' after all.
So yes, they were wrong on all three points.