Hi ChonkySleeper.
Welcome to our Mattress Forum. 
I am SO happy to hear you’re having a great sleep experience on your Luma Sleep Hybrid. You could reach out to them to ask what they think about the potential use of a mattress wedge, since they know their product best and will be able to offer commentary in that regard.
A suitable pillow is an essential part of good alignment for the head and neck and upper body because the gap between the head and the mattress and the curve of the cervical spine needs to be supported just like all other parts of the spine. In your case, because you are sleeping prone the use of a pillow will exacerbate the cervical curvature and twist the spine in that area. Like mattresses … there are certain “needs” that depend on body type and sleeping positions. There is more about choosing pillows in the pillow thread here and the other topics and sources of information that it links to that may be helpful.
I took a look at both pillows you are considering. The Zuma lists the density of the foam they use; transparency is always a good sign. They are using a 1.8 lb polyfoam which is what we would recommend as a minimum density in a mattress, so for a pillow, I would say this is fairly durable. That said, as you’ve noted yourself, our specialty here is mattresses so take what I’m saying here with a grain of salt! I wasn’t able to find any of the foam specs in the Malouf pillow.
It’s important to keep in mind that, with pillows, your personal preferences will also play a much bigger role even than a mattress because it is so close to your face which is very sensitive to temperature, texture, response, and “feel” so I’m not really “qualified” to suggest any particular pillow for someone else when preference plays such a significant role.
I would say that anything Certi-PUR certified is also a good sign. Almost all of the major foam manufacturers in North America are CertiPUR-US certified so if a mattress uses polyurethane foam that is made in North America then the odds are very high that it is CertiPUR-US certified although there are certainly people that may still prefer to make sure that the retailer or manufacturer they are purchasing from is also CertiPUR-US certified (which provides some assurance that their mattresses are using CertiPUR certified materials) just to make sure. That said, keep in mind that this just qualifies the foam as safe but does not speak to the quality or durability of that foam.
Polyfoam is made of petrochemicals, so if you’re wanting to avoid chemicals at all costs, you may want to consider searching out a latex wedge pillow. That said…this will be very hard to find within your budget.
I hope this helps in some capacity. If you have more questions, we’re always here!
NikkiTMU