Florida was called days after the election while Minnesota was called by the end of NBC's and CBS's coverage of the 1984 election(and ABC called it before polls closed in the West)
They were much more aggressive in projecting states back then.
I believe they stopped after the embarrassment of Florida in 2000. The media called it for Gore at first, then called it for Bush, and then switched it back to undecided until Bush finally won it by 537 votes
You are correct. They relied way too heavily on exit polling to make projections back then. It was always flawed, but they got lucky in that it didn't bite them in the butt until Florida in 2000. Several Senate races had been incorrectly projected prior to then (New Hampshire 1996, Georgia 1992, and Florida 1988 all come to mind), but they didn't receive as much attention.