The size of your house (4 bathrooms) would be better served with a 7000, though the 5800 is a very high flow rate valve and it is unlikely you would even notice the difference. Under 2 grand installed for top of the line equipment is a good deal.
The Vortech tank... I am becoming less of a fan these days as we are starting to see some issues in the field, my opinion, stick with a standard bottom screen with gravel underbed.
All RO have "user replaceable filters, "
The guy who didnt test the water, ignore him please.
Considering the high Chlorine level, the 10% resin is highly recommended, I would install a GAC tank as well to remove the Chlorine. Do you really want to bathe and breathe in that chlorine? That chlorine level is what is usually maintained in swimming pools.
I sent you a PM