(There are more open questions in the dictionary. Ones that are specifically about an existing word go in the word's Notes field; to search for them, put "Open question" in the Notes box.)
The adjective/noun distinction
I've written a lot about this in this comment and its subtree. In this below comment, I started to change my mind.
I need to deal with concepts of directness. In English, we often say things like "directly cause" drawing a relevant distinction between that and indirect causation. The distinctions are very important. I should probably have a different verb for that. I already spent
I've discussed this one in the comments on quantifiers. I have no idea what a good approach is.
I have the adverbs