It cut off my last bit, so continuing my post..
Some good reads on separation anxiety are Patricia McConnell's "I'll be home soon" and Nicole Wilde's "Please don't leave me!", both available on Kindle if you want a cheaper version available immediately.
Separation anxiety is something that the finger gets pointed at quite quickly but true separation anxiety is quite severe. While your dog may or may not be suffering from it in its true sense, the methods for dealing with it will most likely help any dog suffering a milder anxiety about being left alone so the books are worth a read anyway IMO.
If nothing else, the shock collar advises you don't use it yet anyway. If you really cannot be convinced not to use one, at least give the kinder methods outlined above/in the recommended books a try first, you may be surprised. And a good behaviourist can be a great resource, and many insurance companies will cover the cost if puppy is insured.
http://www.apbc.org.uk is a good place to find a local behaviourist who will use up-to-date, kind methods.
Another couple of things to take into consideration with behavioural issues - diet can play a huge part on behaviour so I would look at what food you're feeding him and see whether that could be contributing to any issues. For example, highly coloured foods like Bakers can often cause problem behaviour.
Also I would consider his exercise regime. A well-exercised dog may be physically tired but mental stimulation is important too. A 4 month old dog shouldn't be pushed to exhaustion physically while it's still growing, but mental stimulation in the form of obedience and trick training, and 'brain games' can help wear them out - so scattering his dinner across the lawn is a simple way to make dinner time require a bit of brain power, 5 or 10 minutes of trick training in the evening will get his brain cogs turning, etc. When you do take him for walks, consider whether his walks are relaxing or stressful - some activities can raise stress levels, like throwing a ball, but some are more calming, such as letting the dog potter around sniffing. I found that changing what we did on walks helped to relax my dog in the house too.
The general rule of thumb for puppies is 5 minutes of exercise per month - so an hour could be pushing him a bit too far. It's not a completely strict rule, there's some leeway e.g. if you took a slow potter to a park and the hour consisted of sitting down having a rest, some gentle wandering around, and so on, but if you're pavement pounding at a brisk speed for an hour then it's going to put a lot of stress on his developing joints.