Hello. My Name isXXXXX and I would be happy to help. It is often a bit of a task to determine why sudden behavioral changes occur in cats, but it happens more commonly than many feline owners realize. At 9 years old, there are underlying health conditions that have the potential to change a cat's behavior. The most notable of these is hyperthyroidism, a disease where the thyroid becomes abnormal and over-secretes thyroid hormone. Among many other health consequences, hyperthyroidism is know to make cats ornery in some cases.
Other diseases that are known to make otherwise normal kitties grumpy are kidney disease and urinary tract disease. Thus, before making the assumption that this is a behavioral issue, I would schedule an appointment for Jim to have a through examination, blood work, and urinalysis, a small investment of time and money that will either rule out or rule in a medical cause for the odd behavior.
Once a medical cause is ruled out, you can then focus on the behavioral side of it. His territorial behavior directed at the neighborhood dogs may be triggered by the scent of another cat moving into his territory.
Thus, I would try pheromone therapy that may counteract the hostile scent of that presumed other cat that has him is such a territorial and aggressive state.