How to train our small dog not to escape out the front door (and try to attack smaller dogs)?

Train him to sit/stay about 6 ft from the door. Have him sit, command him to stay, go towards the door and if be breaks say NO and go back and correct. Do the same thing with the door bell you can have someone ring the bell while you command the dog. Make sure yo do not open the door until he is obeying. This also helps with dogs barking and jumping on quest