Here's my suggestion on how to fix the situation.

PMtoCoins should convert ALL markets to LTC (and close the BTC/LTC market). This way everyone would be trading with coins that exist instead of imaginary BTC that you currently don't have in your possession. The admin could then trade the collected LTC fees to BTC to pay the debts.

This would make sense, since there are currently several markets on PMtoCoins (BEE, CAGE, CHE, EMO, EMU, FAC, FCK, GRUMP, KARM, LMC, MOON, NUT, PANDA, PENG, RBBT) that are no longer feasible for BTC market and have been converted to LTC markets on other exchanges.

Also I think it's absolutely necessary that you make the current process of paying BTC debts more transparent and organized. You need to post a list of withdraw id's and how much they are still owed. Then you process the withdraws in numerical order, not randomly based on people asking for their BTC. People would know when their turn will be by comparing their withdraw id against the list and also see that you are actually paying them out, although slowly.