What did you pay for him?
I understand this is a distressing incident but you have to be realistic about the claim that you have. You only have a claim for the legal monetary value of the dogs.
Realistically, despite the fact that you paid £1900 a six month old dog is not worth the price you paid for him at eight weeks.
Your only claim is for the monetary value of the dog rather than the sum he was worth to you plus any actual out of pocket expenses actually incurred.
It might well be that £1k is inadequate but you have to be realistic about the sum you can claim.
Can I clarify anything for you?