I started training my 5 month old pup using food. I think that may have been the wrong thing to do. Am I right?

I am having some problems with my GSD. He's five months old and showing almost every sign of aggression and dominance listed on your site. Even as I am typing this he is giving my husband a hard time(growling and barking because he has been forced into a down position and wants to get up). I made the HUGE mistake of buying him from a woman advertising puppies in our local paper ....I didn't know I was making a mistake then...but I have certainly learned a lesson.

This may seem lengthy but I think I need to give you details. First of all I cannot afford training....not at all ..things are tight around here right now. I got him at 4 weeks old ...which I now also know was a mistake. So needless to say I know nothing at all about his parents etc.... Luke (the dog) has been trained to sit,stay,shake,down,high five, open and close cabinets and drawers when told to do so. He was doing all of this by three months old. However ...I think I made ANOTHER mistake by training him with treats ....right or wrong??? Uhhggg I hate to admit that I may have screwed up ....but ...I need advice.

Now that he is five months...he is starting to deliberately ignore what I ask of him(i started off with treats in his training...then weaned him from that and had him doing it when I commanded...his only reward being praise). He is also showing major aggression problems. He bit my seven year old tonight because she tried to take a piece of paper that he had chewed up...it was beside him,not in his mouth. That was certainly not the first time he has done that. He snaps and growls at the children,myself and my husband when we try and get things from him. He only growls louder and gets more aggressive when he is corrected. Sometimes he will actually drop things when told...then there are the times,,,,which are becoming more frequent that he displays horrible "our bursts". I really want to keep this animal,but I also do not want one of my children scarred for life. I understand that my daughter should not have been allowed to take something from the dog....she has been told not to do so. But...on the other hand I can't have the dog biting her that hard or at all because she did something he didn't like. I mean he really bit down..she has scrapes and bruises on her arm. I am more than willing to do what needs to be done at home ....I am not at all afraid of having to work with him.

How can I tell if this is just "normal" dominant behavior that can be corrected or maybe it's something that came from breeding? I fully understand the mistakes I have made where Luke is concerned. But now that I have him I do not want to shuck the responsibility of raising this animal. Not to mention that I love him a great deal. Oh yes ...I've read that neutering may help in calming aggression and might help your dog to not challenge your authority as often. True or False? Any advice to my email address would be greatly appreciated. I understand that there is limited info where email is concerned. I just don't have any clue as to whether to keep this dog or not. I would hate to be one of those people that gets a dog then gets rid of him or her because the dog is not perfect.

If you actually were able to read this lengthy email then I thank you very much,
Angela