Your 3 points actually illustrate perfectly as to why fleets/trade is so poor for the AI and so easily exploited by the player.

The AI spams fleets with no clear objective. It produces them because it can afford to and it techs up to them because it's AI script tells it do so. The AI personalities are linked to the unit/building choices in the production files. That's about all the effect that the personalities have. It's enough though to give the AI the illusionary intelligence that some attribute to it.

Try setting up a startpos with even numbers of ships in all coastal sea regions. Then set the game to auto-run in AI control for about 10 years and see what the AI does with it's fleets. The AI will not form trade routes, nor will it put together lines of ships defending it's coasts and/or linking it's territories. The AI only appears to do this when it has ships in vast numbers. The AI also fails miserably at balancing fleet numbers per sea region and you will often find massive stacks in one sea region and several adjacent regions empty.

This is why I dislike naval fleets and maritime trade as implimented in MTW - not out of any personal bias, but because they simply don't work and don't add to the game in the way that they should. It's just far too easy to conquer the Levant and start raking in a massive trade income. In the past I've often had 1m florin plus treasuries in MTW due to the ease of gaining naval supremecy.