Temp gauge not working?

You need to see if the temp gauge is working. I think the easiest way to do that is with an IR thermometer. They are pretty inexpensive now, and after you have used one a few times, you will wonder how you ever got along without it. If the temp gauge is at the half way point, and the IR thermometer reads 200 degrees (or more), then the problem is likely the temp sensor, the gauge, or wiring in between. If the temp gauge is at the half way point, and the IR thermometer reads 180 degrees (or so), then you know the temp gauge is probably OK, and you can turn your attention to the causes of the leaks.
One way or another, without ACTUALLY knowing the engine's temperature and without being able to reconcile the gauge to the actual temperature, you are (in my opinion) spinning your wheels.