I'm no expert, but my understanding is that ganache typically breaks for two reasons: too much fat or too low of a temperature when agitating. Since you are having more breaking with less cream the fat content does not appear to be the issue for you. So it's probably the temperature. If your liquids fall below 90F before mixing with the chocolate you're asking for trouble. I'm guessing that may be what happened in your previous breaks, especially since it happened with less cream (which was the warm part). You don't want your liquid so hot that you lose your Form V crystals, but you want it above 100F before adding to the chocolate so that you can avoid breaking.
Another trick to toughen up the ganache by the way is to wait until it gets down to about 72F, and then table it for a very short time. I've never done this myself, but I've read that this will make the ganache less soft. Apparently it's really easy to overdo this however, so you want to be careful (and quick) if you try this. But it may help you out. As for the recipes you've seen, those sound like they are intended more for glazes, frostings or fillings. Of course you have to do what works for you, but 2:1 is definitely the standard, and I would give it another test.