A sad day indeed. This pool seemed poised to become the new star. I completely sympathize with your situation though, I only wish more people would realize running a pool properly is serious business.
The only other banner waving in the DGM camp
No need to give up hope, I know of at least 2 pools which are considering switching. PPLNS is also fine, as is PPS if the fees are kept reasonable. There's a promising new pool in the PPS scene, though it seems it wasn't announced here so I'm not sure I'm at liberty to mention it.
When the poolserver has been shut down, the pool will generate additional "pseudo blocks" on current difficulty until your credit reaches less than 0.00000001 BTC.
So you will receive some additional payouts, just like you would have stopped mining for a while.
You are doing it wrong (I mean, this can work too, but there's a proper way to do it). From each miner's score you can calculate his expected pending payout. If the pool closes you need to pay this amount to everyone (like cashout, but with no fee since it is you who initiated the shutdown). By so doing you are paying back the stochastic loan you took from miners when you started the pool. The pool was a model for DGM in life, let it be one also in death.