So it sounds like he is attempting to bite company when they go near doors?
What other behaviors are you seeing?
Is he neutered?
What sort of food is he on?
How much exercise does he get a day?
Yes it sounds like he believes the house is his and he controls the people in it. That is a bit of a terrier type attitude as they do have strong opinions of themselves.
If you could arrange more exercise for him that might help. If he'll play with another dog maybe a play date or two a week to help burn off energy. Some dogs burn off enregy chewing so a stuffed Kong toy or other good chew may help.
You might want to look at the amount of protein he is getting in his diet and reduce it. Many people find aggression issues diminish when they lower the level of protein the dog gets in a daily diet.
If he has not been checked for any health issues you might check for a thyroid problem as that can make dogs irritable or a tick carried disease if those are an issue where you live.
So those are the non training things to look at.
I don't know what other people have suggested to help you with his attitude issues so you may hear some repeats.
It would be good if everyone in the house would start a new regimen with your dog called nothing in life is free. This non violent method makes the humans higher on the status ranking than the dog is. You can read about it here
http://www.paws.org/cas/resources/fact_sheets_dogs/nothingfree.php
Everyone on the same page making sure to follow through on doing this can help.
I think he is viewing humans as lower in pack ranking and so under his control. The above program really can help with that mistaken concept being turned around.
Get everyone to try it for a week and then you should see some results that helps make it easier to keep going for another week with it until it becomes a habit for you all. He can still have treats etc but he has to do something on command first.
If you could read through this and come back to reply with specific questions or info on how others have tried training with you all, that would be great!
I promise I'll get to the meds and how they work for you!
Dog Expert:Rescue, Train,Breed,Care
30+ yrs dog home vet care & nursing, rescue, behavior&training, responsible show breeding, genetics
Thanks for the above accept! Sorry for the delay we just had a big puff of wind go through and the power dropped! Very inconvenient!
For more ease in handling him I'd suggest putting a harness on him with a short tab leash on it maybe 4-6 inches just enough to grab. Or you can add a short tab leash to his collar. Make it one with no loop so it can't get caught on things. A bit of clothes line or light rope with a bolt snap from a hard ware store can work.
For the door opening it sounds like his current behavior is to rush the door and either bite you for opening it or try to bite people coming in. I think training him in an alternative behavior in response to the door bell or a knock might help you. With the new regimen of he has to do something to earn treats this can be a new something for him to do to earn a reward. You can read here about target training which can help with this
http://www.wagntrain.com/Target.htm
Set up a bed or rug for him that will be his place. Have the dog on the leash. Have a friend or your child etc be the 'visitor' who rings or knocks (a cell phone for giving timing directions can be useful here). Knock Knock happends and you take the dog who is on a leash and rush him to the 'place' you want him to go and get him to lie down. It won't be easy at first as he'll want to run to the door. From a container above the 'place' location pull out an incredibly yummy treat to give him when he at least has all 4 feet on the 'place'. You can work up to requiring him to lie down and to waiting longer for his treat until you can go to the door, open it and come back and give the dog his treat. You can at first fasten the leash to someting solid (perhaps someone can put a ring to tether him to where his place is) to help him realize he is to stay there or you can just work on the stay command and use a leash long enough to let you get to the door while holding it.
What you are doing is instead of trying to teach him NO you are teaching him a new response to the stumulus at the door. This new response when done properly earns him a treat, praise, time with a squeaky toy - whatever he really values. The idea is to make it far more worth it to him to perform the new behavior rather than his old one.
You have to be patient putting him back on his place, making him stay, and you may do a lot of knocking or bell ringing before he figures out - wait rushing the door gets me nothing but sitting or lying here works out great for me.
I think you will like clicker training which you can see in video on this site below the ads on the bottom of the page
http://www.clickertrainusa.com/clicker-training-videos.htm
Now the way the medications work - if he gets too wild at the stimulus of the door noises you can use a medication to take that 'edge' off so he can focus and learn what he needs to learn for new behaviors. Clomicalm is one medication used for this and Prozac is another. The key with meds is they are not a cure, instead they are a method of letting the dog be calm enough to focus on the training. Usually you get them as a part of a behavior modification program geared to your dog's needs.
Terriers are very mouthy and one thing you might try is having him bring you a toy to get your attention. If you can find something he likes to hold, and doesn't totally destroy in four seconds, you can make life more fun for him simply by offering him a treat in trade for the toy and throwing the toy for him to chase. Burns off energy, works on your leadership role, and keeps his mouth busy.
Do come back if you have questions and thanks again for the above accept!