Here's what I've got - 26,000 gallon in-ground in Michigan. Sand filter, 1.5" PVC.

What I'm hooking up - 400k btu heater, salt chlorinator, cartridge filter, zinc anode, flow meter. 2" PVC.

My plan - (I welcome advice and criticism) - I want to keep my sand filter hooked up for vacumming, reducing water level & as a backup. I've bypassed the sand filter to not go to heater or salt chlorinator. 1) Should the sand filter also be routed through the salt system? 2) Is the best spot for the zinc anode in between filter & heat. Or basically just anywhere prior to salt system? 3)am I ok going from 1.5" PVC to 2" and back to 1.5" or will I have pressure probs?
Thank you!