Since the Coopers is already hopped you don't need to use bittering hops...for that amount of malt (1 can).
Most cans are 3.3 lbs. You'll need about 4 more lbs of DME to make up the difference.
You will also need to balance the extra malt with your hops.
Is there any reason why you want a high % weizen? Most are just over 5%. I can see making a dunkel that high, maybe (I don't really care for them or Kristall for that matter).
You'll need about 4 lbs of DME.
The LME, and DME for that matter, have already been cooked once. Read up on late extract boils (use the search function). I'd recommend boiling 1 lb of DME for 45 mins then adding all the rest for the last 15.
Good luck.