I see in the cgminer command window that the diff of bitcoin at the moment of posting this is 12.9T, does this mean I need at least 12.9T of hashpower to even consider playing the lottery or do miners with a lot less hashrate get to play the lottery?
You are confusing T with TH , the T that comes after 12.9T does not stand for terahash, the TH on your miner does , without going into much details think of the 12.9T as difficulty point and simply don't pay much attention to it , you can solo mine with any mining gear you have regardless of it's hashrate.
Below is a website made by someone in this forum (forgot who he was but) , you can use it to estimate your chances of finding a block, luck is still your main point of strength when solo mining , but it's good to know the probabilities.
http://solochance.com/