The sudden drop in salinity after the waterchange is most likely the cause for your problems.IMO,1.022 is low for a reef tank,1.025-1.026 is idea.As well as doing waterchanges,it would be a good idea to get some good quality livesand(worms,critters,etc..) and some LR rubble so you can re-seed your tank.You can remove the crushed coral substrate during waterchanges if you want,there probably isn't much life in it anyways.1-2" mixed grain aragonite sand is best for a shallow sand-bed IMO.For a deep sand-bed,4"+ of a fine aragonite sand is idea.