I doubt that the biting is anything do to with his castration, the most likey cause is that you have just let him become leader of the pack. Springers are intelligient dogs (i have one and she has me wrapped round her little paw!). You need to implement some simple rules that will make yuur dog realise that he is not the boss. Always ensure you and your family eat before he does, when you feed him pretend to eat out of his bowl so he thinks thta it isn't his food but your food and you are letting him have some of it. Never let him go through a door before you or a member of your family. You can even try sitting in his bed for 5 minutes a day. Some of these sound silly but this is how a dog at the bottom of the pile would be in the pack situation, they would only recieve leftover once the leaders had eaten, it may seem mean but a dog is happier knowing he has a master. The biting is totally unacceptable and need to be addressed asap, how would you feel if he bit a child? Put the foot down, i know its difficult but you can do it!