(I don't think you can store the userid which is about to be created in the SA_id field, in the same insert behavior
(Looking at your table, I don't understand why you are trying to store the same userid twice in the same row of the table.
If a dealer is the only user who can create a salesperson, then if the FH_id field has a value, then this is the id of the dealer, the userid will identify the salesperson. This row must be a salesperson, because it has a FH_id value.)
However, what you may be able to do is add an update record server behavior AFTER the insert behavior, using the sessionid as the filter ?
I just did a quick test and this approach and it seems to work ok !