Hi jbond04,
There isn’t a formula that can predict which of your options would work best for you in terms of PPP based on specs or theory and I would keep in mind that the only way to know for sure how any of them will feel to you is to sleep on them but #2 and #3 seem to me to be more uncertain and complicated than they need to be and #1 would seem to have the most reasonable chance of moving you towards the softer sleeping surface you are looking for and you would still have the option of adding a topper if your sleeping experience indicates that you needed to. It would also be the least costly.
Not surprisingly I agree with Chuck that the 19 ILD shouldn’t be an issue with feeling too much of the firmness of the support core underneath it.
The better options or possibilities I’m aware of in the Fort Collins area are listed in post #4 here but you would need to check with them to see what types of toppers they carry and their return policies.
Post #2 here and the topper guidelines it links to also includes a link to a list of the better online sources for toppers that I’m aware of but if I was in your shoes I would start with the simplest solution.
Phoenix