I am interested in but cannot find a way to
The easiest way to points 1 and 2 is to have a field that holds that number.
You'll need a scripted or automated field that can update on every new story, or change of epic link on existing stories. Then you'll be able to do JQL like "epic story count < 32", put the number on the cards, and use it as a sortable column in filters.
Point 3 is already in place, if I have understood it correctly - you can say "Epic Link is empty and issuetype not in subTaskIssueTypes()" (Sub-tasks take their Epic from their parent, but don't expose it to JQL, so you need the second clause to say to ignore them)
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