Assuming you don't have bacterial issues in the well water, you should be fine drinking it. But w/o knowing more about the water how do you know if you need additional equipment before the RO system (pretreatment). Iron? Manganese? h2s? metals? You may or may not have things in your well water that will shorten the life of your RO element.
Putting a big carbon tank on well water makes me think he used CGAC to treat h2s. Or maybe he's using it to remove sediment.
3.5 gpm on the concentrate is good - I wouldn't go lower. If you need more permeate flow let me know - there are other tweaks that can be made.
It was a good suggestion above to get it out of the sun - from algae in the tank to degrading the plastics, the sun won't do this system any favors.
Russ