Hi jasesun23,
I would tend to avoid the 1.5 lb supersoft because of the lower density and I would probably choose between the 23 ILD and the 18 ILD. The 23 ILD would be noticeably softer than the 35 ILD base layer you have.
If you spend time sleeping on your side I would probably lean towards 3" and if you don’t then 2" may be enough.
I would tend to talk with suppliers on the phone rather than through email (see post #4 here).
Phoenix