That water should be fine. Although even in smaller systems you will save money in the long term using an RO/DI unit. It just takes longer before the unit will pay itself off. I drive a V8 Mustang so I'm saving money on gas not needing to drive to the grocery store or LFS to get RO water.
That should be fine. RO/DI water is the best you'll be able to get, with a TDS of 0, rather than just low.
RO water should be fine, as long as the RO filters have been serviced regularly. That's what I don't like about buying RO water at grocery stores, you don't know how long it has been since they were last serviced unless you have a handheld TDS meter, which aren't expensive.
I was using culligan ro water for the last year and wow did I have issues, so I tested the water and it was not pure at all,...so frustrating so make sure you just do some quick tests on your water to make sure it has no phosphates and nitrates in it. I finally broke down and got a ro unit of my own, that way I know exactly where my water is coming from, and how clean it is