Yeah +1 to jumping in and getting your feet wet.
But as far as you're questions:
Putting the fermenter into plastic keg tub filled with water will help buffer the temperature swings. It doesn't sound like you're worried about the fermentation being too warm but if you were you could swap some frozen water bottles in the water periodically, like every morning before work and every night when you get home. With a little trial and error on the number of bottles and timing you can get it to hold a pretty constant temp.
By the way the low sixties is actually a pretty good fermentation temp for ales. And a fermometer
on the side of the fermenter is nice to have.
Dry hopping is primarily done to add aroma to the beer. There may be some flavor changes to the beer depending on alcohol content and length of time the hops are left in there but your primary objective with dry hopping is aroma.