I think you might be focusing too much into this one thing, stuck like you said. Ears are super weird objects, and there is a massive variety of them in the world. I think Marc made a comment to the effect that you can do just about anything with them and you will be pretty good to go.
Keep at it, accept that what you draw will look funny at first, and that you will hate everything that you have drawn from just a little while back. Ive got bad pictures posted up on my wall around me and I keep em there until I can replace them with good ones, but I have to fill the wall. Its a fun way to remind myself of the level of progress. And looking back through my archive of older stuff I can find some really horrifyingly ugly drawings from just a couple months ago.
So keep on moving! You don't have to get every part perfect right now, just start to get em down (which you have totally done) and once you have all of the basics down a little bit, just keep on practicing drawing and looking at heads, you will keep on improving!
I noticed a comment you made a little bit ago about shading and color being in a later term, and you are correct. If you want to see a good trick to make simple line drawings look better, I recommend this video here, its fantastic. https://www.youtube.com/watch?v=x0zl5NnEAyU Scott Robertson's stuff is very handy along side Marc's