Is it hard for you to win the spiral cup? if it is just buy a bunch of The lightning strike treasure cards there is a chance they can do a over kill. it will help defeating the last person
You don't need to buy anything; you simply need to plan ahead. And packing your deck with all storm treasure cards is actually a mistake since he does shield (this does not apply to Storm wizards who can use their wand to clear the shield). His 'cheat' can be frustrating, but if you know about it and plan for it, all should be fine.
Easy as pie. Even Randolf the Cheater pig was easy. I didn't use any storm spells either. The easiest one for me was the girl from Weirwood, she only has around 500 health. And, according to the Pigswick Papers, the long line of years Pigswick won the Spiral Cup was the same long line of years no other schools participated.