Firstly, we didn't have quite enough to fill a demijohn so our demijohn is only half full, apparently the more air inside the DJ the worse it is?

Secondly, the recipe called for the apples to be cooked and then left to ferment for a few days (I put in yeast and other ingredients as directed) which I did in our aluminium jam making pan. I have since read fermenting fruits should not be in metal containers.
Since the wine went into the DJ it has not seemed to do a lot and we've not seen a single bubble come through the airlock. I thought this was possibly because most of the fermenting was done in the pan and it was just too slow for us to notice?
I can see bubbles rising to the top of the liquid so there's definitely gases being made!
Is the wine OK to keep? Is there anything I should do?
We have other wines on the go but we're new to it all so any advice would be great.
Thanks!