It dropped to .990, which is what I assume you meant, because you boosted the ABV to around 10.4% making it more of a wine than a cider. Once fermented, all you have left in solution is water (SG of 1.000) and alcohol (SG of .789) bringing the final SG to less than that of water. Since all the ingredients in this recipe are simple sugars the yeast can easily convert everything to booze leaving no sweetness left for you. Now that you added even more sugars for the yeast to eat, it start fermenting again and the SG will end even lower and taste more wine like.
If you want a sweet final product you'll have to prevent the yeast from eating more by either stabilizing with sorbate and sulfites, pasteurizing, adding more sugars until the yeast reach their alcohol limit and die off, or adding unfermentable sugars like spenda depending on your final goal.