Your exegesis of Daniel 9:2 is wrong. Daniel was saying that there were several devastations as you imply but that there was only one such period and that was of seventy years in duration. The use of 'devastations' as a plural form simply denotes an emphasis in Biblical Hebrew and does not imply that there were several periods. The only such period familiar to Daniel would have been the exile and desolation of Judah from the Fall in 607 until its impending finish in 537. Daniel knew when the seventy years began and how long it would last ie. seventy years according to Jeremiah but he would not have known then how this would end.
The Scriptures definitely prove that the desolation of the land was complete because Jeremiah stated that the land would be without an inhabitant or depopulated so this confirms the magnitude or extent of that desolation.