Glad your knife is ok. The tank is a little bit overstocked, but the fish are not full size. you doesn't have high nitrate, the fish stocking shouldn't be a problem yet. I would recommend that you slim the stock down by 25% or so before they grow however. I'd lose the angels and kribs personally.
It is possible for the water to be hard but the pH low. Probably comes out the tap that way. My water is very hard off the charts but my pH is only around 7.4.
As far as the coral, it's just personal preference. It's tacky in my opinion. If you like it, go for it. Us "purists" will just laugh at you, the same way how if you put a hydraulics on that corvette and 24" spinners, corvette guys would laugh. It's just preference.