Hi karalu,
Dunlop and Talalay both have pincores and can look quite similar. The individual pincores don’t go all the way through the original core in either one although a thinner layer may have some that do depending on which part of the original core it is cut from.
A solid non flexing foundation is generally the most suitable option for a latex mattress so the firmness of your foundation wouldn’t be the reason that a latex mattress isn’t working the way you hoped. Even if you replace it with slats, the slats should have as little flex or sagging as possible so that any foundation you choose would be similar to having the mattress on the floor.
Post #2 here and the other posts it links to has more information about the different symptoms that people may experience on a mattress that may help you identify the underlying cause of what you are experiencing but based on your description it sounds like you may need a little softer or thicker comfort layers (or a topper) for some additional pressure relief. Post #2 here has some suggestions that may be helpful if a new mattress is too firm for you.
Post #2 here also has more information about the variables that act together to affect sleeping temperature that may also be helpful. While latex itself is the most breathable type of foam material … the type of cover or quilting in your mattress, your mattress protector or a mattress pad, or the sheets you are using can all have a significant effect on sleeping temperature and may be worth looking at.
Phoenix