You might try and see if Tax Package Support will e-mail you your K-1s that you should have received for SVXY since 2012. Then you will have an accurate idea of the numbers you should have reported on your tax return every year since 2012. Note that just because you had a large gain in SVXY from 2012 on (until this year), does not have anything to do with the partnership activities that are passed on to you. The values of the boxes on your K-1s are based solely on the number of shares of SVXY you held when the parternship activites are distributed. Assuming the partnership activities reported positive income to you over the years, then your cost basis will increase by the same amount so when you finally do sell SVXY, you can realize a bigger loss.
As for when you should realize your loss, that is something that only you can decide.
Good luck and note that Volpocalypse can happen again. I wouldn't touch a product like SVXY.
Thanks again for the free explanation. Yes should of sold JAN of 2018. Perfect case of too much of a good thing. I'm very torn on holding this through this year, but after the crash instincts were to double down. Then SVXY went to half leverage of 0.5x which has hindered those plans yet again. If nobody minds I'll post the outcome of this tax year.