I think there are a number of issues here, and probably the most important is the relationship with the neighbour. If you've done all you say, and you have double glazing, have closed the curtains, and this is not cheek by jowl terraced housing or flats, then I'd be incredibly surprised if your neighbour can actually hear anything. It may be that they have become very sensitised to it, it may even be that they can hear A dog barking which is not yours. Are you able to have a chat with your other neighbours, especially ones who are physically closer to you, and ask them to be brutally honest - can they hear your dog? If the answer is no, or yes, but only occasionally, then you have a neighbour who is looking to pick a fight, not a problem dog.
In that case, I would actually suggest going to see your local Environmental Health Department, who will deal with noise complaints. Ensure you discuss this issue with them and ask them to make a note of your concerns, and ask for their advice. A very large proportion of noise complaints are found, on investigation, to be completely malicious, and are frequently because one neighbour doesn't like another, and simply sees this as a way of making trouble. If you have pro-actively taken the trouble to consult them, record your concerns and show that you are keen to be a good neighbour, you will have built a good foundation if this escalates in the future. If your neighbour genuinely has/had a concern they would themselves contact the Council who would ask them to keep a noise diary, or to have a recording device placed in their home to assess the degree of nuisance. ONLY if a nuisance is proved, can the EHO then issue an abatement order, but that is a very long way down the track and as I said, a huge number of cases are found to be without foundation at this stage.
There is NEVER any excuse for bellowing at you in the street - you must have found it very upsetting.
Now back to the dog! Do you think he actually was barking all night? Could you leave a recorder/video camera with him to see what he is actually doing when you leave him?
PLEASE, PLEASE do not use an anti barking collar - no reputable trainer would use them, and they can be very counter productive. Thankfully, shock collars have been banned in Wales and generally these kinds of aversive training techniques are being dropped by all reputable trainers (thank God) as more research emerges on how dogs learn. Positive training methods are far more effective. On the issue of company, I personally like this. Dogs are, by their nature very sociable animals and some dogs do much better in a multi dog household (that is not to say that solo dogs can't be happy or well adjusted). But personally, I would concentrate first on finding out if you genuinely have a dog problem or a neighbour problem. It might also be helpful for you to consult an accredited behaviourist to help with the already excellent progress you are making on helping your dog to settle and adjust to their new life.
Lastly, please don't underestimate the fact that this is the weekend before Bonfire NIght. Therefore, there will be a massive amount of fireworks going off, and many dogs who are otherwise model canine citizens will be barking much more than normal, because of all the very loud bangs.
Good luck. [hsmile]