Thread rises from the dead--Maybe Final, final post:
Ford IBC: from my reading the Ford IBC only reduces brake signal at speeds under about 10 mph for a less jerky stop. The manual lever never reduces out for vehicle speed. Research from owner manuals over several years seem to indicate that the low, med, high aggressiveness setting showed up in the 2015 trucks. Ford makes a replacement IBC module that has an "improved" part number. Research with a Ford Service department indicated that installing the improved part would still not add the aggressiveness setting that I so desired. I really wanted to find a solution that would react to the amount of brake petal push, but finally gave up.
Prodigy P3 report: so I finally decided to try the P3. I could use the Prodigy adapter cable for a smooth plug in but I would need to have a Ford Service department deprogram the computer so it wouldn't through an error message for a missing IBC. So, I decided to manually install the P3 parallel to the IBC. I had to run all 4 wires to the sources and tap into the correct brake petal wire. Since I have the inside bed trailer wire connector in addition to the typical one mounted at the bumper, I split the brake control wire between the too connectors with the bed side to the P3. I now have two complete trailer brake systems that work depending on which connector that I plug into. Measuring the IBC max voltage back to the trailer (set just below tire skidding), I set the P3 gain to match. I found that the B1 boost setting would turn on the actuator at the slightest petal push--what I've been looking for! On the first test drive yesterday, I found the B3 highest boost gave the best balance between truck and trailer. It is not as smooth as IBC, but the more aggressive braking at a low petal actuation is also what I was looking for--this is the best solution that I've tried. And, I feel that I'm going to have the best emergency braking from this setup. Maybe someday I can afford the $70,000 fix--a new truck.
Bonus: I have a backup brake controller in the IBC if something goes wrong with my P3 installation.
Anyone interested in installation specifics may shoot me a private email.
Thanks for all the help along the way.