Need towing advice - managing transmission temp (gas engine)

[RhythmMachine]

We took our 2012 35ix (ZF 8HP45 transmission) out with the trailer (about 3500lbs loaded) this weekend for the first time. My previous tow vehicle was a 2009 MB ML320, which was a diesel with a 7-speed transmission. Between the lower torque with the X5's gas engine (about 100 less) and the 8-speed transmission, I was concerned about how the transmission temp would be. I also have an intermittent issue where sometimes the gate will open up to let me shift into sport/manual mode, but often it won't, in which case I'm stuck using automatic mode and the transmission is shifting as often as it wants... which is really often.

I had to be in full automatic mode for most of the trip, but was able to get into manual for much of the return. Ambient temps were around 20-25C, engine temps were usually 100-110C, and my transmission temps were usually 100-108C. From what I've read, normal operating transmission temp should be 80-100C, with the max allowed for short duration (like climbing a large hill) is 135C.

Interestingly, after I dropped the trailer off and was driving home the transmission temp had dropped about 10C while I was sitting, but once I started driving it rose to the same levels I had while towing and stayed there... so I'm not sure if it's actually getting any hotter while towing than not.

I expected to see a significant difference when I was able to get into manual mode and reduce the number of shifts, but it didn't have much of an impact.

So, I have a number of questions that I'm hoping those of you with more knowledge and experience will be able to help me with.

1. Should I be concerned about my current operating range? I was consistently running a little above the the high end of "normal", and while there were a number of significant hills (southern Alberta), the ambient temperature was lower than it will be when we're doing most of our towing in the summer. I'm not sure if I was over the normal range because the car couldn't cool it adequately or if it was "intentionally" running in that range, since it didn't continue to climb.

2. I'm at about 160K km on the car and the transmission fluid hasn't been changed (I bought it this past winter), so I have an appointment with my trusted indy shop to get that done at the end of the month. Will fresh fluid impact the temperatures much?

3. When I get the transmission fluid changed, I opted to go with the VF OE oil pan and filter, which is plastic, but several hundred Canadian dollars less than an aluminum model. I've read lots of people saying that the aluminum pan "should" have an impact on lowering the temp, but no real-world input from people who have used both with the same car/similar circumstances. Does anyone know if upgrading to an aluminum transmission oil pan will have a material impact on keeping the temp down and so may be worth spending on?

3. I got a VEEPEAK OBD dongle and Car Scanner Pro to read it to see when the torque converter is locked up, but it doesn't seem able to pull that value even though it lists a sensor for it. Bimmerlink doesn't list that sensor, so maybe it's not possible to monitor. I am able to monitor the transmission's output shaft speed and turbine speed, though... am I correct in assuming that if those are the same, the torque converter is locked? Running in 6th gear at around 100km/h both values were often sitting at 288 rpm, but having it there didn't seem to impact the operating temp much. I also read somewhere that when the fuel efficiency gauge is at about 1/2 way or lower (which, on a Canadian model would be 10L/100km), that indicates that the torque converter is locked, but I couldn't find any way to keep it locked in that zone at highway speed with any kind of incline. If keeping the torque converter locked is important, how can I do that and tell when I'm doing it?

Thanks!