While your knowledge of cars, DIY projects, and modifications are commendable, I caution you in advertising the rate at which you are exceeding the regulated and rated capability of a 200.
Yes, we can all agree that 200s are conservatively rated; however, stated weights, capacities and capabilities are stamped by Toyota for a reason.
If you were to ever be at fault in an accident, especially one with your large trailer, I suspect that you would not have the accreditation/approval to substantiate your modifications.
Between 35” tires, spacers, homemade trailer hitch welds, and 15,000# combined weights, you wouldn’t stand a chance in liability court. Particularly against someone or an insurance company with any sort of technical acumen.
My $.02