Use a digital thermometer you use to measure fever. They are cheap, fast, easy-to-read and usually water-proof and they have to be quite accurate; 100F/37.8C is a typical fever . (I currently have 37.3C due to swine flu ! Not as bad as advertised.)

The water bath can be a tad warmer than the process temperature, as the bottles and tank are not completely submerged and agitation in air brings temperature down. Say, 102 or 103 F.

Measure the actual temperature of the developer before starting, not just the water bath. It takes surprisingly long to heat if you are just using the process waterbath. Use warmer water to make this happen faster, and when it's at 100F, then move it to the actual waterbath and wait a bit to stabilize the temperatures.

But, I don't think that the main problem is in the temperature. What you describe sounds quite bad. Color crossover can be caused by temperature error, and too low temperature indeed causes cyan cast (due to the underdevelopment of the bottom red-sensitive layer), but that is not something you easily see with bare eye when looking at the negative.

I still suspect the blix. Although the Tetenal C-41 blix has worked flawlessly for me and many others, it's said that it's not easy to make proper film blix. And, Tetenal has failed the RA-4 blix also, so I wouldn't be surprised if that was the cause.