Thank you for your question regarding your 3 year old Male mix breed whom you have been having some nasty aggression and biting problems with very recently. First and foremost I would like to urge you to ensure your dog is not able to have direct contact with strangers for the next few weeks, and that you also be very careful with him around other dogs as well. This may seem a little over the top, but it is definitely better to be safe than sorry in these situations and I'm sure the last thing you want is for him to be taken away by dog control! In order to get control of this situation you need to show your dog that you and your family are alpha dog over him.
If you treat your dog as an equal it may well see it as an opportunity to challenge your position. For example, be aware that allowing your dog onto the couch, bed, etc will give it the leeway that it needs to be able to challenge your position as the alpha dog in the relationship. This behavior change may occur quite gradually, without you even noticing it, until your dog starts showing aggressive tendencies when you try to move it!
You should reprimand your dog for unacceptable behavior, no matter what that behavior is. If you do not reprimand your dogs poor behavior then it will feel that it has the right to behave that way and it will take much longer to correct the behavior. What I recommend you do, is the next time your dog acts poorly and exhibits dominant tendencies (growling), saturate your dog with the garden hose or a bucket of water, or if it is inside, throw a heavy blanket over your dog and be sure to reprimand it. DO NOT yell, as this has no effect on the dominant dog. Growl instead, use a guttural growl like " AAHHH!" instead of "No!", as this makes a sharper sound then "No" (If done correctly it may hurt your throat a little).
The following techniques to reinforce your status as alpha dog
Whenever your dog barks, snarls or acts inappropriately around other people (as you have described in your dog's history) and dogs, you instantly need to reprimand him as above.
You don't really mention how well trained your dog is but I assume from your question that it has had some background in obedience work. Either way I would recommend that you start training your dog on a regular basis and under a variety of conditions.
The progression below is a useful one that many people have used to get better results from their dogs. The first step is to have your training session in an environment where your dog is comfortable and not threatened. You can decide where you start on the progression if you feel that you would get a good response out of the earlier progressions and do not need to do it again.
You will also be the best judge of when you should move on to the next progression, but I would recommend that you move on when your dog completes a 5 to 10 minute sit-stay and a 5-10 minute down-stay. This may require you to go back to the beginning to quite basic commands but you are better to take things slowly and complete this program over a number of weeks.
1. inside, on-leash, with no other dogs or people present,
2. outside, on-leash, with no other dogs or people present,
3. outside, off-leash, with no other dogs or people present,
4. outside, on-leash, gradually introducing dogs and people to the vicinity,
5. outside, off-leash, gradually introducing dogs and people to the vicinity.
In the mean time I would definitely recommend that you keep your dog well away from small children and other dogs other than while you are completing this training, so as to avoid as many potentially bad situations as possible. The more exposure your dog gets to confrontational situations the harder it will be to fix.
Outside of training it may be worth trying to socialize your dog a bit more. Preferably with friends who have dogs of calm temperament, as they will be more forgiving of any incidents! In saying that, if you think that your dog may react badly by biting or fighting then consider using a muzzle. Again, this will have to be a gradual process where the new dog is introduced at a neutral venue and from a distance. By that I mean you should get your dog to sit and have the other dog in your dogs sight but a long way away. You want to keep your dogs focus and attention on you as your friend gradually brings the other dog closer. If your dog makes to move from the sit then have your friend back off to reduce the distraction. Once your dog is comfortable around other dogs, you may be able to convince some brave children of friends to help with the training to get him used to being around young people.
Here is a specific program to deal with your little dog rushing to the door when visitors arrive.
Get an adult friend to come and visit (make sure that you tell them what is happening!).
As your friend knocks on the door or rings the doorbell, make your dog sit and give it a treat. Then put your dogs collar on and take it to either a crate or a secure room. If your dog is too much of a handful at even this stage then you will have to put your dog away before your visitor gets to the door.
Sit your friend down in a room that is not often use by your dog. Give you friend some treats so that they can give them to your dog.
Go to your dog and make it sit. Put a halti or muzzle as well as the choke collar on. Get your dog to heel then take it into the room that your friend is in. Make sure that your friend does not give any eye contact. Act as happy as you can while petting your dog.
If your dog growls or disobeys your commands at ANY TIME then squirt it with water or shake a pebble filled can to startle it. Have the water pistol or can in your dogs view at all times.
Make your dog sit quite a long way from your guest, perhaps in the doorway of the room. When your dog is calm get it to heel and move it closer, then get your dog to sit again. Praise your dog when it sits and heels properly.
When your dog is calm and you have moved it and made it sit within 5 feet of the guest then get the guest to give your dog a treat. Make sure that the guest does not look your dog in the eyes.
Preferably you will repeat this twice a day for several weeks. That may not be entirely practical for you but will give you the best chance of success. This method requires that your dog knows and responds to the sit and heel commands. Make sure that your dog does this before you attempt this method.
If after several weeks he is still absolutely uncontrollable, I would definitely encourage you to visit your Veterinarian to get some behavioral altering medication to help you with his training. Dog that are too fired up are very difficult to get control of without some medical help. Clomicalm is ideal for this sort of situation and you should ask for this by name if you are having a lot of trouble after a couple of weeks. If after 2 - 3 months of the above in depth training and changing of his mindset he is still isn't improving you should give him one last chance by taking him to a behavioral specialist in your area. Then if this extra help does not seem to be doing any good, then the next step would be to get him humanely euthanised. But I do believe that every bad dog deserves a chance and with patience, persistence and praise I am sure you can convince him to change.
Best of luck with your dog and please let me know how you get on.
Dr M D Edwards