I think its a good idea to draw bigger when you want to learn to proportion things but it can be difficult inking larger pictures. Also do you have a thinner pen, I think that would be better to use on the hair and facial features. Also you could try inking using gimp, it's something I started doing recently, it's more forgiving when it comes to mistakes unlike inking by hand. But it takes some time getting used to, a laptop pad is like using your finger as a pen so it's easier than with a mouse but I don't know what kind of computer you have. Other than that I think you're doing fine. Keep putting stuff out ^_^