Your LO sounds a lot like my son who just turned two in the middle of July. We started with an eval through our regional center for his speech delay - at 20 months, he was only saying 4 words. When the lady came out, she thought there might be a bit more going on and she wanted him to get fully assessed for autism. He was sent to a clinical psychologist who spent an hour and a half with him, labeled him as autistic and went on her merry way. I'm not saying I disagree with her diagnosis, but truly, only a neurologist should be putting that label on your son. I know your post was a month ago, but if your son is still behind in language, I HIGHLY recommend the Baby Signing Time DVD's - since we started my son on those, his language has exploded - he knows about 100 words and is starting to put two word phrases together - all this in about 4 months. He also headbanged - but violently. He would throw himself on the floor and then arch back like he was winding up and slam his head on the ground - the wood floors, the tile, the wall, even the cinder block wall in the backyard. He would also spin around a lot. Like your son, his eye contact is good, but it's like his hearing is hit and miss - at least when we call his name. If a train is going by though, he hears that just fine!
My husband and I were super hesitant to have him labeled because the minute you tell someone else, "My son is autistic," you get this sad "oh I'm so sorry" look on their face. So we tell people as we need to, but mainly tell them the "symptom" if they raise an eyebrow. We say "he has stranger anxiety" or whatever it might be. However, he did start Early Intervention services right away two months before his 2nd birthday and WOW, what a difference. It has helped his speech and tremendously helped his behavior. He used to have these violent temper tantrums, and as you said - they were for no reason or what we considered "stupid" reasons, but he would generally calm if he got his way. I have a few friends who work with autistic children and I'm a high school administrator myself so I have people around to ask questions and help out. Everyone agrees, early intervention is KEY. Call your local regional center to have them do an intake to determine if he qualifies for services. If nothing else, he'll qualify for speech. They might provide other services as well - take whatever you can get. It certainly can't hurt your son to have extra "teachers" around to help him! If it comes out that he is in fact on the spectrum, continue the services, particularly if your son's markers are "mild". My son is very high functioning - knows all his letters and is a whiz at puzzles and everyone that's been working with him says in a few years, we probably won't even be able to notice the markers that labeled him as autistic to begin with. He will always be on the spectrum, but the early intervention will help curb the negative behaviors that he displays and highlight the positive ones. We even went so far as to put him into the "pre-school" with ABA therapy. There is also a website, rethinkautism.com that provides parents with supplemental lessons to work with kids on the spectrum.
I know it's hard and you don't want your son to be labeled. At first, I felt kind of "cheated" that all these other people got perfectly healthy "normal" kids and my son wasn't normal, but I take one look into his gorgeous blue eyes and I wouldn't have it any other way. It's a tough pill to swallow, but I totally understand where you're coming from. No matter what you take from this, I highly encourage you to start early intervention services. If it turns out to be absolutely nothing, then all you've done is help your son get a leg up on his peers by having more one-on-one tutors at this young age! Good luck to you and your son!