I understand your frustrations with other members of the household, perhaps you can talk to them? I know it's difficult, but let them know in a tactful way about your fears for Nicholas.
You can do a bit of training with recall and keeping loads of treats with you- FIRST do this in the safety of an enclosed area such as your back garden- let him out and then call to him with the treat, reward him with lots of praise and with the treat when he comes back to you. Do this repeatedly until you are confident with him... then take him to the park or somewhere else and do it there. Then do it at your front door. Recall is the most important things to teach your dog, it can save his life.
There are other techniques to train your dog recall, but this is how I did it with mine. Also you can just teach him to stay away from the front door, so he won't even go near it when it opens and closes.
Maybe other members will have better ideas or advice for you. Good Luck and let us know how you do.
Desrae, guardian of two tri-coloured cavaliers, Belle 3 years old and Bobby 1 year/8 months.