again bro, hyposalinity is 1.008-1.010..
to answer your questions:
1. at hypo salinity, skimmers doesnt work the same as in normal salinity.. your better off with an airstone and airpump..
2&3. sometimes in my QTs, i use an airpump and a foam filter only.. plus some wave maker.. or an overhead filter na dual output, 1 for water circulation and 1 dun sa filter.
4. mapapansin mo lang.. most important is monitoring ammonia.. pag steady na ammonia, change it 1-2 times a week..
5. i dont really QT my CUC but you can.. especially corals from the wild.. ang daming nakatagong parasites and HH sa mga wild caught corals.. but make sure hindi hyposalinity, sufficient light and good parameters..