Hi JackBauer,
Thanks for the kind words 
Just as an addition to my last reply … when you are comparing mattresses it’s important to make sure you are comparing apples to apples and that the type and blend of latex is the same. FSF uses 100% natural talalay so their 12" queen latex mattress here would be comparable to SleepEz Organic 13000 here. The SleepEz Natural 13000 here uses blended Talalay so it wouldn’t be an apples to apples comparison.
There really isn’t a down side to having a a split top layer and it can provide more flexibility if you need to make changes to one side of the mattress down the road (the mattress will last a long time and you never know what your circumstances may be years from now). With a good wool quilted cover it would be very unlikely that you could feel the split and if the sides are the same ILD then you also won’t feel a transition from one side to the other (see post #2 here). As you also mentioned it gives you options to configure and fine tune the layers the layers that you wouldn’t have otherwise if you used solid layers. If you are at all concerned about the split you could also use a single soft top layer and then split the others below it but this isn’t really necessary.
At your weight a 12" mattress wouldn’t really be necessary although some people may still choose it as a preference (see post #14 here about the potential benefits of thicker layers or a thicker mattress)
Phoenix