I could understand the the forward collision sensor issue when the rear end squats due to the tools. It’s not really blocked but instead aimed upward or straight ahead since the truck is more level or even nose high when loaded down. That can be adjusted with a little bit of time and effort. It’s a common adjustment, think about how many lifted f150’s and raptors there are.
As far as the noise goes, I would throw some grease on there. Bushing with a lack of grease or lubricant will always squeak.
Then why doesn't the truck throw this alarm when they're leveled or going up a sharp incline while off road or hooking my boat up. I've taken mine to my deer lease and it's leveled with no alarm. Some of the hills I go over are steep and it's like approaching a wall. My Ski boat makes the back sag a little but never caused any alarms
I Think there's a bigger issue here. If 500 lbs causes the back of his truck to settle enough to raise the front that much, there's a problem.