Hi lebaryo,
It can take a little detective work and more detailed conversations on the phone to track down the underlying cause of your symptoms and any layering changes that have the best odds of correcting them … especially if you are outside the averages that work for most people of your height and weight.
Post #2 here may be helpful to eliminate some of the other possibilities that may be contributing to your symptoms and I would check on the effect of your mattress protector and unzipping the cover as well as your pillow but the most important suggestion is a more detailed conversation with Sleepez so they can help you identify any changes that have the best odds of success.
I would be very cautious about adding another soft layer to your mattress because having 6" of soft latex would generally be too soft and quite risky for alignment for someone of your height and weight.
Phoenix