Based on the dimensions, 2x 3/16" beer lines and the fan look like it should fit into a 2.75" hole without any problems.
I would think you have enough cooling ability with what you have but it's possible to increase the air flow at the expense of fan life. (If you put a 12V DC power supply on the fan it will push more air but it's generally not designed to run continuously at 100% operating load.)
I'd say test it and see if you like it...although that could be considered alcohol abuse if it doesn't work.
Good luck.