He may indeed like you back. After all, he did respond to your video.
If he didn’t like you at all, he most likely would not have sent you that message.
The problem is, he may not quite know how to go about interacting with you.
He may not quite know how to deal with a girl that he just recently found out has a crush on him.
In essence, he may just feel a lot of unease and anxiety.
That may be the reason for the awkward conversation after he saw your video and even the awkward smile in the hallways.
He just doesn’t seem to be comfortable.
Something that you could do is try to work on your body language.
Try to make it more inviting the next time that you talk to him.
Try smiling more, laughing more and having more consistent eye contact with him.
Also try to mimic his posture.
In other words, if he is slouching, copy that.
If he is upright, copy that.
If he is leaning into you, copy that.
Mimicking another person’s posture will often help in making them feel a lot more comfortable around you because it is as though you are letting them know that you are just like them and there is nothing to be intimidated about.
Try making these body language adjustments the next time that you interact with him and he may start responding in a much more positive way towards you.