You could take the gosling. Their care is pretty easy. There's waterfowl starter food available. Chick crumbles will work in a pinch. Goslings also like to crop grass. If the geese have not hurt this gosling they may be alright. It's a hard call; you have to decide if yo want to raise...
Yes. This happens, occasionally, with first time parents. Unfortunately it may repeat with each new breeding attempt. From your description it sounds like the hen is the culprit. You can try removing the gander if there are more eggs hatching, but be prepared.