Oh, the dread of a first haircut. It is always shocking when they cut off the dark hair, and hand you a light colored dog that you barely recognize. But, even though you were not quite ready for it, the color change is inevitable, and part of growing up. If you prolong it, it can also look weird with part dark and part light. The hair certainly will grow back, but it's going to be light, and it's just a sign that your puppy is growing up.
But, the good news is that he is absolutely adorable. It's good that you found the ear infection and treated it. Some of the other itching may be due to fleas or allergies, and the biting around the butt could also be due to anal gland being irritated or full.
You should try to get comfortable with doing a little trimming on your pup. I'd suggest getting some scissors with rounded tips that won't hurt him. I especially like these for trimming around eyes, paw pads, private areas,and for removing little matts and occasional debris:
Amazon.com: TINY TRIM ball tipped small pet...