You will have to enter the information transferred fro the Brokerage firms manually in order to allocate the Gain or Loss equally in your wife's and your returns (50/50). So, unfortunately there is no easy way to do this.
Additionally, you will not be able to include an explanation when you e-file. If you would like to include an explanation on a certain position you have taken you will have to send a Paper Return accompanied with Form 8275 in order to explain the allocation and avoid any Penalties for underreporting.
Form 8275: https://www.irs.gov/pub/irs-access/f8275_accessible.pdf
Instructions: https://www.irs.gov/pub/irs-pdf/i8275.pdf
