I looked at your sketch and, unfortunately, I know nothing about the jeelib library and can not comment on what power savings you should expect from that.
However, assuming that everything else is perfect, you have a relatively large current drain with your sensor wiring. Because it is always powered the current (in mA) will be
Isensor = 1000 * 3.3 / (560 + Rsensor)
so, if your sensor is 560 ohms, you will have a continuous current drain of approximately 3mA. This does not explain the large drop you were seeing, but running at 6V I'd say your radio is probably toasted, flash too (if you have it), and they would be a very large current drain. Did you actually get any radio signal?
Tom