It takes time to regain condition if a snake's been housed or fed improperly. For that weight I'd think you are fine on one mouse every 5 days then one every 7 days once it's hit 200 grams or so. When the snake is a bit bigger 2 every 7 days would likely be the next logical step. If at some point you want to move to rats, that's your choice but I wouldn't mess around with anything right now in case it triggers a refusal. If the snake is eating, stick with what is working, worry about changes in prey type later. Healthy weight is weight gained regularily over time by feeding top quality prey.