The ground around the house is deformed and distorted. The well exists, sort of, half sunk down the wall of the great sinkhole which has opened up. Accessing it again will be difficult. Whatever treasures are down there may be lost, unless you're feeling risky and want to cliffhang over the bottomless pit.
Your destination is indeed the Dragon Tower, deep within the veil. The closest city is Roanoke, and there should be a small village and trading depot en route if you want to make a bit of a detour. It would be good for the purpose of selling and identifying things, though word is that the trading depots are a bit more expensive/frugal than the cities for the services they provide.
The rat swarm is already heading off down the road, leaving just Drosselmeyer behind. The old rat's face is buried in maniscripts and maps as he is trying to make sense of a personal quandary. "The well, the well, I remember it... not well. All I recall is fear and hate from it. The Baron's wife was mauled by that thing, that thing in the well. So he went to fix her hand so she would be beautiful again. That's all I know of it. Even though the Baron I am not, I feel a sense of relief knowing that whatever it was, it was sealed up tight. I doubt it will be freed now.
Do what you wish with the keys, for the house is no more.
I suppose I will be off then, if there is nothing further to do. Farewell humans." He gathered his maps, flinging them over his back, and began a long walk down the road.