First batch of pee questions

[Minnesotamaker]

Have a couple of questions about backsweetened wine and ABV. My starting SG was 1.070 and final SG when fermented dry was .990. I sweetened to an SG of 1.008. How does this affect the ABV?

1) do I go by volume and since I added 12 ounces of sweetener to 1g (128 ounces) do I just reduce the total ABV by about 1%?
2) since the SG raised about 2% on the hydrometer did I reduce the ABV by 2%?
3) what % of "residual" sugar do I now have?
* I did a little research and think my residual sugar is about 5.7%

Adding sugar won't really change your ABV. I guess "technically", it would change it slightly. ABV is a measure of alcohol by volume, so by adding sugar to a finished batch, the volume will change slightly while the total alcohol present will not change. Since the sugar won't change the volume of wine very much, I wouldn't worry too much about it. Measuring alcohol using a hydrometer isn't an exacting way to measure alcohol anyway.... close, but not exact. Adding sugar at the end won't change the alcohol content as long as you've stabilized your batch with sorbate and sulfite.