Increase Pipe Feeding softener

I have a softener fed via a 3/4" supply from a pressure tank and I still get some rust on my fittings. I was thinking off adding sediment filter post softener. There is a 1" line from well to the tank. The pressure switch is 30-50. I was going to add a sediment filter after the softener. So my though was to increase the pipe size to 1" up through the filter then back down to 3/4". I talked to a guy from the local water district during an open house and he suggested I put the filter (Larger 4" filter so I have more surface area to filter) after the softener (let the softener do most of the filtering) and then you do not have to change it as much as if it would be installed before the softener. He also though it would be OK to increase the supply pipe to the softener. Any Ideas?