Unfortunately the queen is now dead, after seeing her staggering around I found her dead the next day. I have been in contact with a PhD student studying Dinoponera at Leeds University and asked her opinion (although a different Genus, they may have similarities?).
here is her reply.
I don't have any experience of that species specifically, but I've found with my Dinoponera colonies that worker mortality is quite high, and I've had quite a bit of trouble trying to get the colonies to a point where they are at least replacing the workers who are dying. In my species, the egg stage seems to take only a few days, and they then remain larvae for several weeks. Once they've pupated it takes another 3 - 4 weeks for the adult workers to emerge, so its quite a long turn-around from egg to worker. I've also found that they have quite a high death rate of eggs and larvae - from what I've heard the Queen will lay 1-2 eggs a day, and in my colonies that tends to translate to 3 or 4 larvae a month. As I said, I don't have any experience of working with Paraponera, but if they are similar to Dinoponera, then with such a small colony to start out with, its quite possible that the death rate simply exceeded the birth rate.
Do you know if Paraponera reproduce by fission in the wild? In Dinoponera, the Queen is not capable of raising brood on her own, and so new colonies are only ever formed by a small number of workers splitting off from a larger colony. So if your colony got down to only the Queen, that might explain why she wasn't producing any brood. (Sebastian; This does sound similar to what Randy Morgan from Cincinnati Zoo has written about).
I've found that my colonies have been very susceptible to fungal infection, and I lost a few colonies due to that last month. I had been keeping them in plaster nests but it seems this provides a perfect environment for fungus, and now I'm keeping them in plastic nest boxes instead, and they seem to be doing much better. I've also found that they need quite a bit of variety in their diet - I was initially just feeding them meal worms and the occasional bit of fruit but I found that after a while they weren't really taking the meal worms, even though their larvae were starving - I've started giving them tinned meat about once a week (they seem to really like corned beef) and since then the colonies are doing much better.
Her next question was that she hoped that my experience wouldn't put me off trying again, as i am really bad with money i expect to be taking out a bank loan soon.