Personally, I'm not seeing the value in getting it down to 10% that's still a pretty dang big beer. A "one and done" as my wife says, either way.
If I absolutely had to drop the ABV, what I'd do here is follow the kit to the letter, then deliberately over top-off to about 6-gallons, and (this is critical) split the batch into 2 buckets/carboys. Reduced ABV, almost no chance of blow-off, no wasted fermentables, and extra bottles of beer.
For the oak chips, i would put them in a shallow plastic container with the bourbon 6oz is plenty, but make sure to use enough booze to cover the chips. When the time comes, dump the container booze and all.