How to proceed? 2nd pitch or not?

A four point drop over three days wouldn’t give me confidence that it’s done fermenting. However, the US-05 might be finished/kaput due to the ABV. Assuming your gravity readings are accurate and corrected for temperature, your beer was at 11% ABV before the added bourbon and reached the published alcohol tolerance for US-05, which Fermentis says is 9-11%.

Given the tolerance of US-05, adding more at this point might be fruitless or (worse) stressful on the newly pitched US-05. It might help to add a different yeast with a higher alcohol tolerance, like Nottingham (14%) and let it ferment out, or add some LalBrew CBC-1 at bottling.

Bear in mind that my comments are supported only by what I’ve read and not by practice.
Hopefully someone with more knowledge/experience with this can lend some insight.

 

I’ll ask what the recipe is.
What temperature are you fermenting at. Often I will ramp up the temp to 73-77 just to see if the yeast can do a little more. Does not always work, but often it does.

When I am making a big beer I have found, at times, that it can take 3 weeks in the primary before it’s truly finished.

I will transfer to a secondary fermenter when using wood, nibs, coconut fruit or any other extra ingredients just because it’s a old method, which I still like. Others may say it’s not required, but I like it and it works.

Ripper is on point with the extra yeast at bottling. I’ve used that yeast a lot when the brew is 11 abv or higher with good results.

Good luck.