The video doesn't show us what we need to see. Have your partner rock the wheel like you did in the video but slower and wider sweeping. Is the rack moving as if the bolts aren't tight enough? Let's see the input shaft and a tie rod in the same frame within the video. Are the control arm bushing...
A standalone EPAS controller is only way to retain EPAS. I have a sport mode version that is plug and play while keeping the rack in sport mode. You can find it here. https://wireeverything.com/products/ols/products/2005-14-mustanggt500-epas-controller-single-mode.
This is a complete solution...
The Hi-amp kits are now $159
This connector isn't correct for what you were trying to do, it is a 4 pin. What you have pictured is the mate to the fan motor connector.
I would talk to my engine builder or tuner; it would be surprising if Boss cams couldn't get the job done while retaining VCT. I want to say your stock cams are capable of it, but am not 100% how hard you would have to lean on the engine to get there.
Turbo is going to be the way to go here.
There is a lot of weight to come out of the car yet. If you're serious about weight reduction you have to realign your ideas about noise and vehicle harshness.
2-piece brake rotors
Wheels and tires
Suspension component material (aluminum vs steel)
Headers vs manifolds
Rear seat belts and child...