HELP! My wine has stopped fermenting prematurely?

I am making my first wine which is not from a kit. I have been following a recipe but seem to be having problems.

I began putting my mushed up cooking apples along with yeast, yeast nutrient and Pectolase in a fermentation bucket with an airlock fitted to the lid. This started fermenting vigourously but then stopped after 3 days. In the hope of getting it to start up again I added the sugar, some citric acid and some more yeast and nutrient. This got it fermenting like crazy for another 4 days before stopping again, which just happens to be the day it's due for it's first racking. I proceeded to strain the wine through muslin, as instructed, and put it into a demijohn. I used an airlock on it and hoped it would show some signs of life... but nothing. So I hastily added more sugar, citric acid and yeast (like before), stirred it like crazy and still nothing.

I now believe I have added too much sugar (the sugar sediment at the bottom of the jar is a bit of a giveaway) and I am completely at a loss as to why the fermentation process keeps stopping and what I can do to salvage this wine (if anything).

Any advice from wine makers will be very much appreciated!

Thanks.