Like the others said, get your pressure fluctuations under control first with a proper tank. Then, if you still have problems, you can use a tempering valve to accurately regulate the temperature in the hot water system.
Here's an example:
http://cgi.ebay.com/TACO-3-4-Sweat-Mixing-Valve-5003-C2-Tempering-Valve_W0QQitemZ230325501272QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item230325501272&_trksid=p3286.c0.m14&_trkparms=72%3A1205%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50
As for water softners, a modern demand based unit will have much better performance than the older one. You can go to Lowes or HD and pick up a test kit to test the hardness of the raw water coming out of the ground. Add this to the anticipated GPM water use and you can find the appropriate system. As far as I know, all softners use salt brine to strip the ions out of the resin core. A few years ago, I put together a green sand filter and a water softner from CSI to deal with sediment in the well water. Both systems are self-managing except for adding salt and neutralizer.