With regards to #1, I'd buy a Hach 5B hardness test kit so you can test your own water. Then, if you have a triple-tree type bypass, just mix unsoftened water with softened until you raise the hardness to 5~7gpg. Trial and error on the amount to bypass, using the hardness tester.
And for #5, I can't see it being a big issue for a home owner, either. Perhaps in commercial apps, or where equipment requirements force the user to remain under a few ppm... but if I had it in my home, I wouldn't worry, personally. I'm sure the pros can give more examples where it might matter a lot.