How do I prevent white film forming on utensils in dishwashers?
is it wise to spend on dishwasher maintenance and water softeners when we have the water with too much hardness (900 ppm)?


Well, the whole point of a water softener is to reduce the hardness. So I find it odd that you ask if it's wise to use a water softener when your water is excessively hard... In short, yes, that's what you do to fix this problem, normally - install a water softener with appropriate capacity to deal with the hardness of your water, at least for the appliances you care about that for.