I'd skip all the other steps and just add the dregs to the portion you want to sour. Wine yeast is only an issue if it is competing with another sacc strain, not a concern for secondary fermentation. You don't need to make a starter. I recommend adding oak last. It's easy to overdo and a year is a long time for a small amount of beer on even a few cubes. I usually boil my oak first to get some flavor out. If you want a beer to taste like fruit, add the fruit after the base beer is where you want it. Adding fruit early ends up with less fruit flavor. For a really good fruit sour, 1lb pet gallon is my minimum, 2 lbs per gallon is the standard, and I've used up to 3 lbs per gallon.
The only thing worse than dumping beer is serving beer you should have dumped.