A way to deal with the standing water in your lines is to install a circulation loop in your hot water line.
This involves taking your hot water line near to the Jobo installing a tee and running a line back to the bottom of your hot water heater. Normally the drain fitting in the bottom of the heater is removed and reinstalled in a tee that is placed in the drain opening. The circulating return line is then plumbed into the other opening in the tee.
Depending on the distance, sometimes these work very well through convection without the addition of a circulating pump and sometimes a circulating pump is required. Again distance is the important consideration.
For precise temp control at a reasonable cost, I would look for one of the older Arkay tempering units to show up on Ebay...possibly check with Midwest Photo or any of your used photo dealers locally. With a lot of labs going digital this equipment is probably being pulled and thrown away.