No, re-torquing those bolts won't hurt a thing. Might even fix a leak.
Don't know much about Cool Guard II, as I no longer work at a John Deere dealership. But it's definitely not the old G05 formulation. The label calls it a tri-organic formula... whatever that means.
In general (but with a few exceptions over the years), I trust John Deere engineering. I was impressed with their products and support compared to other equipment makes that I've worked on. But IF (and it's just an 'if' right now) they've switched to a 2eha coolant, then I'm going to have to either reevaluate my opinion of Mother Deere or eat crow.