Got little to no idea about average ambient temps in NZ, but tweak'e has probably hit the nail on the head.
The degassing thing ? As the fermentation proceeds, the yeast produces alcohol and CO2 as bi-products - both have different levels of desirability. The CO2 mostly sits in the ferment as dissolved CO2/carbonic acid. All the time that the ferment is going (however small), some of the yeast debris is moving around, which create "nucleation points" for the carbonic acid to attach too as gaseous CO2, which are the bubbles that are seen at the airlock i.e. when the ferment is going hard, newly started, etc there's more stuff floating around. I'd guess that the movement will have disturbed some of the sediment, enough for the bubbles to start to appear, albeit slowly. Plus it takes time for small amounts of pressure/bubbles to build up enough for the airlock to release the gas.
Also, degassing is a method to remove the gas after the ferment has completed, as the dissolved CO2/carbonic acid can give a bit of a "tang" to the batch. So it can be removed with a little vacuum or even gentle agitation (I think that the device is called a "wine whip"). The vacuum creates an inverse pressure thing that helps "pull" the CO2 out, the wine whip moves the sediment a bit to allow the gas to attach to the debris and rise out as bubbles (some people like to stopper a carboy/DJ and then shake or roll it around - obviously some carboys/DJ's are just too heavy to do that).
There is usually a noticeable change in taste once the gas is all cleared out.
As for hitting this batch with sulphites, I'd go for it, because while it depends entirely on the starting gravity, your honey to water ratio at the start would suggest that there might be a little fermentation left to go, but it also might be finished - those hydrometer readings suggest that it's either finished or pretty close too.....
The colder the temp of the batch, the more carbonic acid/CO2 gets retained (think of chilling coke, lemonade, etc and how much CO2 gets released when opening, as opposed to how much "fizz" you get when opening one that's at room temperature).
