Hi lilac2,
I’m not dodo of course but I thought I’d add a few comments that may be helpful until dodo sees your post.
I would keep in mind that ILD with memory foam is not particularly relevant because memory foam ILD isn’t comparable to any other types of foam and the ILD of memory foam also changes with temperature, humidity, and the length of time that the topper is compressed.
Just in case you haven’t read it yet … post #2 here and the topper guidelines it links to may also be helpful.
I’ll leave the rest of your questions for dodo to answer 
Phoenix