I agree with rebecca. Full evaluations by a team of professionals who have experience in diagnosing autism will either rule it in or out.
The variability of him sometimes liking to be lifted high in the air and at other times screaming and being scared, could be down to Sensory Integration Dysfunction. Google it to see what it is. But basically the sensory system is not performing as it should and there can be variations throughout the day and day to day. My son also would sometimes climb dangerously high, yet at other times would scream if his feet left the floor. He also is sensitive to noise, yet at other times appears deaf. His sense of touch is oversensitive at times and yet at others he feels no pain. It can also affect the sense of balance and propriocpetion (where our body is in space), this is the sense that might be affecting your son if he is so variable when his feet leave the floor. An Occupational Therapist is the person to assess for this. SID is experienced to some degree by everyone on the autistic spectrum, but you can have SID and not be on the spectrum as well.
I'm not expert but the fact that he was born with a cyst sounds to me like he might be having autism-like symptoms because of complications from the cyst. However, the fact that he is having issues is reason enough to have him properly evaluated by professionals, starting with a good speech therapist. Now is definitely the time to get him into speech therapy and any other therapies that can help him with his various delays in development. It wouldn't hurt for you to look into intervention strategies like ABA or Floortime too, since they help with interacting with socially delayed children whether it is from autism or not. As the grandmother of a 5 year old with autism I can't stress enough how much early intervention has helped. Aidan has a real shot at an independant life because of early intervention (it's not a guarantee, but he's responding well so far). So definitely, pursue a diagnosis of some sort because it sounds like your little guy needs some extra help to achieve his fullest potential.