I'd like to use the arrows for movement, though that's not a big deal. The game doesn't save my weapon selection over sessions. Pressing 'e' from the inventory should close the inventory. I like the 'ready' screen playing every time you resume; good choice with that.
Last level I just keep trying til I hit the king, then I put a block on the bottom of the triangle's platform. It still takes luck to hit the king, but once you do that it's easy.
I used the middle civilization, went all physical (+max xp except against the bosses) except on the octopus, where I used lightning storm to take him down to 0, then hit him with a unit to finish him off.
Hard mode in 25 levels, but it gave me credit for only 13. I don't see how you could do it in less rounds, since there are 25 on the most direct path to the end.