We are in a simultaneous discount state as well, but the 50/50 split twist is new, however I think I can still help.
Example: Owner's Title = $800, Lender's Title = $600, Simultaneous Issue Fee = $50
The end math needs to work out so Borrower pays $450 and Seller pays $400.
Under Section B or C (depending on whether the Borrower shopped) you enter the full Lender's Title at $600.
Under Section H (Other) you enter the Owner's Title at $250 [800+50-600 per 1026.37(g)(4) Commentary] in the applicable Seller-Paid column.
In Section L under Seller Credit enter $150 [400-250]
With this Seller Credit the Borrower ends up paying $450 [600-150] for Title Fees.
It's not pretty but I think it is compliant.