Catch off guard

Hello,

I would really appreciate any advice you could give on my Patterdale Terrier.

His name is Gizmo, he's four years old. We got him as a rescue dog and we are his fourth owners. Before we got him we have heard he was owned by drug/alcohol addicts and has been beaten. Gizmo is scared of everything from wheels, walking sticks, people, noises etc.

He has always guarded his possessions but lately this seems to have increased, he guards anything he likes the look of; is there a way I can stop him from doing this? The other and worst thing he does, is biting people, mainly my mum who he has bitten around 5 times, however this is usually when my mum has been drinking alcohol, I was wondering if it stems from his old owners getting drunk and beating him? Gizmo was 10 months old when we got him and at first he seemed to improve but now seems to be getting naughty again, he only really listens to me and that's only 90% of the time.

I've tried writing a list of 'Gizmo' rules for my mum to follow to help Gizmo understand that she is also a pack leader along with me, ie. not to feed him off her plate or not to let Gizmo on her bed.

The reason I am so desperate for advice is because my mum says she has had enough and that she is going to take Gizmo to be put to sleep this week, I really can't bear this happening as I love him so much and I think he's a good dog he just needs the right guidance.
I know I could get a dog behaviourist but they are so expensive and I'm on minimum wage, plus as Gizmo doesn't do the bad behaviours constantly it would be hard to show the trainer the behaviours.

Please help, any advice greatly appreciated.

Many thanks,

Hayley, by email