Seeing as how it appears to need to be shifted to the left (3rd picture), you may end up with a minimal gap on your right side of the pocket. Regardless of this, make a block that will fit in the neck pocket, same height as the top and re vise the neck to the body and it would be a good idea if you had two long straight edges (at least 3' long) to hold to each side of the neck, following the neck taper and going across the body as well, re-mark it and route as necessary.
In the future, don't rely on a single center line, I use a set of straight edge rulers (both 4') that follow the neck taper, all the way across the body and always make fixes that look like you intended them to be that way
All in all, I think you'll do fine with this fix, it's all up to you now
