How to create a new record from a parent item and no longer display that parent as an option to prevent duplicates.

I can try to help, but first can you restate your question.  We do not need to know the field list for every table unless it is relevant to the question as that just adds to much mental clutter to posting a clean question.

What would help is to understand the tables and their relationships, ie, which is the One and which is the Many for each relationship.