the PTP should have provided you with a sales schedule that will allow you to compute the capital gain/loss on disposition. sadly only $3,000 of net capital loss can be used in a year. we can't see what you entered each year from the k-1. ordinary loss on line 1 would be netted with rental income on line 2 (and any other items of passive gain or loss. if the net is a loss for the year that loss is not deductible (you needed to check the PTP box on the K-1). then the loss from that year is carried forward to next year and any net passive loss for the following years would be accumulated and be deductible in the year 2020 when you made a full disposition. you must check the box for full disposition. you also have to enter some sales info. the 1099-B does not have your correct tax basis that can only come from the PTP sales schedule after taking into account any ordinary income on disposition. Your tax basis would be the amount in the column labeled cost basis + the column labeled something like "gain subject to recapture as ordinary income"
on the k-1 sales schedule enter on line 5 the gain subject to recapture as ordinary income, line 7 basis = 0
line 9 the same amount as on line 5. this will flow to form 4797 line 10.
