The point of checking the SG is to be reasonably certain that
fermentation has stopped. If you're below the target SG, and the wine
is no longer bubbling, then fermentation is finished, which is good.

At this point (as the instructions should tell you) you should be
adding the clarifying agent(s). Most kits also have you add sorbate
as a precaution, in case there is any residual sugar. What I don't
understand is why you would want to add sugar before you bottle. If
this is a dry red kit, why not leave it dry?

If you are going to sweeten it, then you definitely need to add the
sorbate, to prevent renewed fermentation. If you are going to leave
the wine dry, the sorbate is optional. It shouldn't hurt, but you
shouldn't need it, based on your SG readings. In any case, don't be
in a rush to bottle it. Particularly if you do sweeten the wine, give
it a few days to adjust and settle before bottling.

Doug