West highland terrier aggression problems

I just moved in with my husband and my mother inlaw who happens to own a nightmare of a Westie. He is extremely aggressive and territorial. My husband or I can't even look at him without him growling and coming after him and forget touching. He also feels the need to pee all over everything, rip up anything paper that goes threw the mail slot and cry and carry on all day.

The only time I can get near him is with food and he comes to me for that and even if I give him food once it's gone thats the end of him being nice towards me.

HIs aggression towards me and my husband keeps getting worse and worse and nothing seems to stop it. I don't want to force my mother inlaw to put him down but he's not safe to be around even if hes only small. I'm worried he'll randomly start attacking other people what should I do?

Hi, I wouldn't like to be in your shoes, even little dogs can be very scary when they are aggressive. Westies are stubborn little things, but I wouldn't give up yet.

I have a Westie, and a well behaved one at that, but only through constant disipline and the establishment of a clear pecking order.

There are a number of things I would try:

1) Get the dog de-sexed - this will likely calm his personality

2) get a water-gun! Westies hate water, when he's playing up squirt him and back it up by scolding him with a sharp, strong and deep noise.

3) Never look up to him, stand up straight and look over him.