You shouldn't, theoretically, need to keep a close eye on the KH/GH...once you know what it is coming out of your tap, then unless there is some drastic change from your water company/nature then it will remain either hard, hard/soft, or soft.
I would keep feeding to 4/5 times a week initially, feeding only enough that your current fish wil eat within 1/2 minutes...overfeeding is a major cause of alot of accidents, mishaps and problems.
I have soft water, and that's okay because it suits the fish I am keeping/going to keep.
I will def keep an eye on the feeding as well. I was more under the impression that what they can eat in two mins was okay, but if it's better to start off more like 30 seconds, than that's okay.