@bakkart Haven't used it yet, but I noticed a walkthrough button on the main menu screen, since you were asking about it. Perhaps this can tip you over the edge with the troubled areas?
@bakkart #7 was the last challenege on my list also, its a lil bit tricky to drop the ball on the best spot... hard #7 was easy again.
I needed 5 or 6 attmepts do master the challenge. Max out soldier skills is useful (although, in my sucessful attmept only 3 enemies reach them).
I had also maxed out my trap skills, but i think that's minor.