1)There should be a valve at the return pipe from the overflow, try to tune it so that the water lvl in the overflow is higher and this will greatly reduce the noise.
2)Dun think the cabinet will give way, what is the material of the cabinet? For the rusting of hinges, u can print over it or change every year, quite hard to stop rusting.
3)Get a clip on fan, it should work better then computer fan, but u will need to top up DI water more often, as evapouration will increase.