Hi buzzdrew7.
Welcome to our Mattress Forum. 
So sorry to hear that you are unable to get comfortable on this mattress. A split configuration would have been a great decision, and is something to keep in mind for future consideration.
For now, finding comfort on your mattress is a priority. ​
A good quality topper can be an effective way to add some additional softness. Toppers are designed to add comfort to a mattress that too firm and needs some pressure relief qualities (which yours does). When you use a topper over a mattress the topper will compress and in combination with the layers below it will take on the shape of your body profile. Softer toppers will compress more than firmer toppers. This “cradle” formed by the upper layers re-distributes weight away from the pressure points of the body.
Sometimes choosing a topper can be as difficult as choosing a mattress as it takes a bit of trial and error to dial in and find the exact combo of support/comfort best for your needs. The good news is that if you do end up making a suitable topper choice and the mattress/topper combination turns out to be a good “match” for you in terms of PPP then it also has the advantage of being able to replace just the topper without replacing the entire mattress if it softens or breaks down before the upper foam layers in the mattress (the upper layers or a sleeping system tend to soften or break down before the deeper layers) or if your needs or preferences change over time and a topper can also help extend the useful life of the mattress underneath it as well.
There is more information about choosing a topper in post #2 here and the topper guidelines it links to which along with a conversation with a reliable and knowledgeable supplier (that can provide you with good information about how their toppers compare to each other or to other toppers they are familiar with that are available on the market) can help you use your sleeping experience as a reference point and guideline to help you choose the type, thickness, and firmness for a topper that has the least possible risk and the best chance for success. It also includes a link to a list of some of the better online sources for toppers I’m aware of and a link to the online suppliers that have good exchange/return policies as well (just in case the topper you choose doesn’t turn out as well as you hoped for).
There are also some suggestions in post #2 here that may be helpful if your mattress is too firm as well.
I would suggest looking into DIY latex layers with someone like Arizona Premium and asking about their layer exchange policy so that if the layer you select isn’t right, you’re able to do a little trouble shooting.
NikkiTMU