There are a ton of methods out there for speaker cone repair. Cracks can be sealed with clear nail polish, though it dries very rigid so is probably going to take some flex away when used on large cracks. I have a jbl with a hole (pencil size)... it has been patched with elmers and toilet tissue - very sparingly. No ill sonic effects. I have also used rubber cement on small cracks in the cloth surround. It is more flexible, but won't last quite as long as other methods. The key is to repair/touch lightly... don't over do it. The only real reason to patch those you've shown is to make them less fragile so that they don't become a big problem.
I wouldn't bother trying to fix dents in the dust cap. Those will not have an effect on the sound. Also... clean them if you must. I've used a dry tooth brush to free dust and dirt, but frankly, if doesn't bother you looking at it, leave it alone. More chance of f*cking things up the more you touch the speaker.