Names are normally split into LName/FName, else you start getting into LIKE operators in queries. Also, if there are two actors with the last name Jones, you may only end up with only one of the records if you do such a LIKE comparision. If you don't have LOTS of records already, the easiest thing may be for you to copy your table, then dump all the single field names into a spreadsheet, then use the Excel text to column wizard to split your names and copy these and Paste Append into your copy table. If you can do that yourself, you'll save time by not waiting for a working vba procedure to split the names for you. I'm assuming your names are divided by some sort of consistent character (,) or space. The odd one might give you problems (such as LL Cool J).
To address your other questions is not really possible, given not much is divulged about your tables and relationships. Sounds like you might benefit from some normalization reading: Normalization Parts I, II, III, IV, and V http://rogersaccessblog.blogspot.ca/...on-part-i.html
(and a lot of other stuff if you're really new to relational databases in general).
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.