Can you get a picture of the frog's cloaca? It looked like there was some irritation. It may just be the picture, idk. When was the last time he pooped? You may have already said and I just missed it.
This might be a bit gross, but have you noticed any sort of smell from him? With your frog excreting white liquid I might worry about infection (most intestinal bacteria have a very distinct odor). It's more likely a kidney problem like Lija said, but if it were an infection that advanced you'd want to get antibiotics ASAP

Another side effect of feeding too many mice is liver problems. Since he looks like he might be toxing out, there might be something going on with his liver causing him to not be able to filter toxins well.

I remember a thread a little while back where someone's frog was having seizures from overdosing on a calcium supplement. Could that be part of what is going on here? The frog has been getting a food with calcium in the bones also dusted in calcium...

btw, I used to have well water. I never used it for my frog because I've had it kill fish before. Also, I have run experiments comparing water bacterial contents, and well water has a LOT of really nasty bugs in it.