I decided it was time to bite the bullet and replace the system. I had done the usual things with the circulating pump (changed twice) and the bearings ont he circulating motor (just replaced last November). I thought briefly about the AO S Vertex, but decided that may be too much for me to handle. The tank was still under warranty (15 yr) so, I am going with a new Marathon (85g elec) as can't easily install the two new vent pipes for a DV WH...will also put in a Lennox G61V. My AC is fine so will reuse. After the warranty, Lennox, utility and tax credit I will have slightly over 2k invested. I am at a point where I just don't need to deal with a system that was as unstable as it is/was. Thanks for all of your help.