Ron,
You sound like an innovative individual. My feeling on the milky oil is that with an oil change or 2, you are getting most of it out, unless it's getting back into the
compartment with every rain shower. A check at the drain plugs may reveal clean water, after the machine has set outside for a while. It may not be cavitation you have, usually more of a pulsing sound to it. Once working, the hot oil will out-gas any remaining moisture over time, but in the interim, of course, it's hard on machined surfaces.
I've never heard of a B oil cooler leaking engine coolant back into the shuttle oil, and likely you would recognize it in the oil as you start to drain. However oil coolers have been known to leak one way and not another, despite what seems logical.
The next machine I get, that I suspect has a plugged pump screen, I'm going to drill and thread for a pipe plug, maybe a 3/4", not sure. This should allow the area under the screen to be flushed(note debris in pic), possibly allowing the screen to be cleaned somewhat, by you and future owners. Not recommending this but I will try almost anything to learn. The bottom of the screen is about 1/2"- 5/8" above the floor of the torque tube. Just to the right of one of the 'blue' plugs, sealing the openings to torque converter, is the opening the pump pic-up tube uses to reach the bottom. Here are some reference pics. The shuttle assembly has been removed so you can see the countershaft and gears, as well as the end of the pick-up tube. Phil