"I am trying to work on altering the crossover point of the HF driver in this Altec network."
I think of resistors in this tweeter circuit as attenuating the volume, not altering the crossover point.
It's a 2nd order high pass filter with the capacitor managing the cutoff frequency, and the coil shunt making the cutoff slope steeper. Changing the crossover point would require changing the Cap and Coil values. Yah?
Check out this simple calculator page. It's not gospel but it is simple.
https://www.v-cap.com/speaker-crossover-calculator.php
Using the calculator I see around 1250 Hz as the Tweeter crossover point. In the 2nd Order Calculator, I chose Linkwitz Riley, and input 1250 Hz, along with your 16 ohm Tweeter. I assumed a 8 ohm woofer, and you'll see it delivering close to your 4 uF and 4mH values in the Tweeter filter, and reasonably close to the Woofer values.
Look at the L-Pad attenuation calc for changing the volume. That would help you determine the right Pot for adjustable attenuation. Any chance the value for R2 is 2.5 ohms not 25? (also, going full OCD, I would label the R going to Positive as R1 and the shunt as R2)
“You needed a new pancreas. The one we bought for you frees you from a dangerous dependency.”
Armitage