[ewill3rd]

Based on what I see, you have had 4 problems with the car to date and one problem with the dealer mishandling your vehicle.

I had another car that was not working correctly on the passenger seat airbag or "PPS" system. (passenger presence)
The PPS may need to be recalibrated or it may need a new sensor.
The one I have seen in my shop, I replaced the PPS module and sensor, it's part of the lower cushion. Remember the person in the seat needs to weigh a sufficient amount, but on the one I had my 190 pounds wouldn't trigger the sensor at times so we acted on the side of caution and replaced it.

They appear to be addressing your issues as they arise. A "lemon" is typically a car that has the same problem more than 3 times without a resolution but I am sure the definition is broader than that.
I would agree calling Cadillac Customer Care and expressing your concerns is a good idea. I doubt they will feel as if your problems are outrageous, but I am sure they will be more than happy to talk to you about them.

It seems as though your dealer is trying to help you out, but salespeople have a different mindset. I bet if the General Manager knew about your situation and you told him they tried to offer you half the value of your car on trade with 5,000 miles on it he'd be yelling at someone!
I wouldn't hold that against the entire dealership though, just the guy who offered you that bogus deal.

I hope they fix your problems.
Let me know how it goes with the airbag system, I'll give you more advice on that if you need it so you can get it fixed with your dealer.