I'm not sure about weight. Lucy is about 30" long Awesome is about 25" long the mice we feed them are about 2-1/2 to 3 inches long (without tail) she calls them hoppers.We feed based on the girth of the snake. I'll get some scales soon and be able give more info on my snakes when I need help.
Thanks,
Jamie
25" sounds like some where around 350+ grams, but that length to weight isn't accurate, as for the food item, yah a small rat pup or weaned rat sounds right.. small mouse should be no problem. I would say give him some time to adjust, maybe a week or so.