2. Check the pH. Test kits are cheap and there is some advice in the packet.
3. The leaf curl on the lemon and the grapefruit will not be the same leaf curl we associate with nectarines and peaches (that's a fungal disease). It could be citrus leaf-miner which you'll have to look closely to see. Google it for remedies. If I am stumped on symptoms or want confirmation I do an image search on google for a match.
4. Best advice that I can give for taking cuttings is to get some rooting powder. Not the type used in city clubs but the type you can get in Bunnings when you buy your pH test kit. Whack your cuttings in some sharp sand and give them some gentle bottom-heat. Again just to confirm - some gentle heat under the container you are striking your cuttings in. Sometimes I just put them on the concrete path overnight because it holds a little heat. Or bring them in overnight.
Air layering is another idea that I think has been mentioned already by P2W.
