Hard Water, Undersized Loops, Missing Hydro Separator? Failed TT-399

I currently have a triangle tube prestige - 399 which failed last week (great timing I know). I had this unit for 3 years and its predecessor for 7. The more I have dug into boilers the more I believe is done wrong.

MY SETUP:
399 Boiler

Triangle Tube Smart 80 (76 Gal) Indirect Water Heater

6 High Temp Zones (5 Air Handlers + 1 Baseboard Radiator)

2 Low Temp Zones (2 In Floor Hydronic Loops)

PICTURES

https://imgur.com/a/rNICrOc
Questions:

1. My water is very hard, could this be causing buildup in the floor loops that is getting stuck in the boiler? If so, how can I flush everything out or what filter should i have?

2. Is a hydraulic separator necessary?

3. Is the current magnetic filter limiting the flow of the main loop?

4. Is the main loop undersized (currently 1.5 Inch)