I was on the wrong side of that last second score change 3 times myself. Would've beaten medium 7 long before I did if it weren't for them taking out my towns in the dying seconds. My favourite has to be when they blocked my capture of a town that would've secured victory on 96%, forcing the game to a stalematey.
Great job doing hard 7. I think success on there is very much based on how everything starts off. If you can keep them away from that gold-giving town, and then pick fights with the nearby towns so you can keep upgrading your ship you've got 'em beat most of the time. That being said, it was a dying minute scramble around the map for me too. I left nothing to chance and took out every town I could, and thankfully they were all level 1 or 2 still because of their lack of gold.
If you need a hand with the multiplayer boosting let us know on here and I should be able to help out (probably next week would be the best and earliest opportunity if you're interested).