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On your questions:

1. There are two important numbers for partnerships:  how much "capital" you have at risk, and how much "basis" you have.  Your basis is the sum of nonrecourse loans plus your ending capital account.  But your capital at risk is only looking at your capital account.  So if that's negative, you no longer have capital at risk.
2. Since you said line J was all positive, I assume you did a partial sale?  TT will release passive losses to the extent that there is offsetting income, so if you have adequate losses they should cover your ordinary gain.  Suspended losses will only be released completely, and be available to offset other non-mlp income, when you sell completely.

One final note:  if you have no capital at risk, but still have basis, your statement about "negative capital account is taxed as a capital gain" isn't quite right.  Distributions "in excess of basis" are taxed as capital gain.  But if you still have basis, that doesn't apply.  What DOES happen is that a bunch of your losses are going to get suspended on form 6198 -- a special purgatory for losses that you won't be able to ever use unless you add more capital to the MLP.  So if you did a complete sale there's a portion of your losses that can't be claimed.