Good post but the descriptions of the chocolates are a bit vague for me. I presume semi sweet and unsweetened are high cocoa solid products. eg bars that contain 80% cocoa solids and not your 'ordinary' Dairy Milk. Our dog nicked a chocolate bar a few Christmases ago and we rang the vet for advice, when we told he the dog had eaten a high cocoa solid bar she asked how quick could we get to the surgery - it was 11pm on a Sunday to give an indication how serious the vet thought it was. Dog was fine as we'd already induced vomiting but it was scary how concerned the vet was.
On the other hand, we had a customer last year whose dog had eaten a full tin of Quality Street and the only side effect was colourful sparkles in the poo for days after as the dog didn't bother unwrapping the sweets.