You need to coordinate with your ex. You can report half or can report it all (there's a workaround in TT for the 1099-S, if he reports it all).
The 2nd, and actually bigger, issue is "depreciation recapture". He can (and should) report all the depreciation recapture, on his return, since he was the one who claimed all the depreciation in the past. But that means he wants to claim all the capital loss, too, to offset the depreciation recapture.
