A note on the chain. You don't remove a link when it's too worn. You replace it. Chain has a pitch of 1/2 inch so what you can do is use a 12 inch good quality ruler with fine lines. Line up the edge of a pin at one end and look at the other end for the pin there to line up at the same place. If it's over by up to 1/16 it's OK or near to gone depending on how close it is to being a full 1/16 inch too long. If the pin there is past 1/16 inch then replace the chain without question.

With a crankset it's often hard to tell when the teeth are worn too far. I then to go with how much of a hook there is on the pressure side that hooks and pushes against the chain rollers. With a lot of use and wear this edge mushrooms over and you can hook a fingernail on the curl of metal along the edge of the tooth.

At the rear it's much the same thing again along with carefully looking at the shape for signs of bad hooking. But with modern teeth it's often hard to tell for sure if they are misshapen or not since they are highly unsymetrical even new out of the box. So what most of us do is ride them until the chain starts to skip over the teeth due to not being able to lay cleanly in the gullets. You'll first feel this when riding up a steep hill or when going for a big burst of speed in a small rear sprocket.