No, he is looking at the sky divers that he went up to talk to. Just because you do not know who is off to the right does not mean that there was no one there. They were not magically teleported in at the last second.
Just admit that you were taken in by right wing sources and move on.
Actually as Commander in Chief it is proper for the President to salute soldiers. At least it has been for a while. It was first done by Ronald Reagan and has been polite gesture of the President ever since:
He does not have to return a salute since he is not in uniform. It is a way of picking out and honoring individual soldiers or a group of soldiers.
Again, how do you know? I have not checked that out yet, but you often cannot see what a person is reacting to. For example when Trump waves to nobody some groups have gone out of their way to catch multiple camera angles to show that there is no one there.