18 to 20 brix is pretty easy to achieve if the cane is ripe. By this I mean that the cane is harvested in the fall or winter and that the cane is properly topped. No need to leave the growing point and top leaves to dilute the juice. Your 80 moisture probably is fairly accurate. The problem is having the proper equipment in order to maximize extraction. My small 3 roll cane mill can do about 20% extraction of juice by weight on the first expressed juice. If the bagasse is put back through the cane mill, a total of 30% or so can be realized. Other modifications I'm sure will increase total extraction such as a shredder, all adding to equipment cost. So, assuming a 30% extraction, 2000 lb of millable cane should yeild 600 lbs of juice or 85 gallons of juice at 18 to 20 brix which should yeild a wine with around a 12% alcohol potential. This should convert to about 10 gal of 200 proof ethanol, theoretical maximum. Remember, in a production sugar cane mill making sugar, the bagasse leaves the mill after total extraction at about 55% moisture. They maximize sucrose extraction by adding back water to help release the last bit of sugar.
Hope this helps.