Hi Ana,
If I am understanding you correctly you are planning on trying (from the bottom up) your 4" air mattress and then 3" of 30 ILD 100% natural Dunlop in the middle and then your 2" 24 ILd Talalay topper as the top layer.
Most Dunlop molds are 6" thick but there are a few companies that make molded Dunlop in 3" molds. If a 6" core is slit in half then the bottom 3" would likely be a little bit firmer and denser than the top 3" layer that was cut from the same core but there are ways of compensating for this so the difference may be slight.
The ILD of latex is tested and rated on the full core and then any layers that are cut from the original core would be rated the same as the full core regardless of the thickness.
There is also more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support” and “pressure relief” and “feel”.
All the layers and components in a mattress will affect the feel and performance of every other layer and component above and below it and your configuration is so different from the layers or mattresses that you tested and there are so many unknowns and variables involved that there really isn’t any way to know whether the combination you are considering will be a good “match” for you in terms of PPP outside of your own personal experience.
Phoenix