Maybe I've found a strategy for the last level, at least it worked for me:
try to arrive at the last flagship with almost the entire crew (at the maximum upgrade, 160), then head over it and attack it in close combat, and keep firing with cannons. You should be able to beat it even when the support ship arrive.
Hope it helps.
Once again, another great game ruined by just one mission...
And the most difficult part is to deal with the CPU overload that slow everything down with a P4 2,8HT at minimum detail: please, it's not Crysis nor UT3...
This is how I did for challenge 4 (after 1000 times):
put shield on follow on sword. Then move just sword trying to form a triangle, possibly moving it in circles around dragon. In this way shield should be closer to dragon and get its fire. Another useful move is suddenly changing the direction of sword keeping shield between sword and dragon.
Thats the way I completed it, but it's still difficult.
I hope it helps, but that challenge ruins the game: making it so annoying it's not challenging, just frustrating.
 "Creeper World 2: Academy"){kind=icon}
 "Neon Race"){kind=icon}
 "Topsy Turvy"){kind=icon}
 "Endless Migration"){kind=icon}
 "Stick Arena: Ballistick"){kind=icon}
 "Dreams"){kind=icon}
 "Mud and Blood 2"){kind=icon}
 "Jumpcat"){kind=icon}
 "Kongai Launch"){kind=icon}
 "Balloon Invasion"){kind=icon}
 "Treasure of Cutlass Reef"){kind=icon}
 "Bot Arena 3"){kind=icon}