Deleting old kernel modules manually

Basically I like to have a "clean" system; so I run the ubuntu-tweak janitor from time to time to delete the old kernels. Today I did some manual checking and found the subdirectory 3.13.0-49-generic within /lib/modules, That is fine it is my current kernel on 14.04; and yes, I want all the modules in there.

But then there are two older subdirectories 3.13.0-32-generic and 3.8.0-31-generic that contain various files like modules.alias, etc; and in the 3.8 directory, some really old vbox ko files.

Also when I run dkms status I am told:

bbswitch, 0.7, 3.13.0-29-generic, x86_64: built
bbswitch, 0.7, 3.13.0-49-generic, x86_64: installed

I have two questions:

1. I assume it is safe to just delete the last two directories?
2. Why is the janitor not deleting that older module for bbswitch; and how would I delete it manually?