I think everything is already said.

You should use movie sequences as backgrounds to get more animation instead of simple pictures.

You should watch real movies about what you are trying to do like superman, iron man, spider man, etc. then see how actors moves during they are "flying" to give the illusion that they are really flying, they don't just stand like a plank ;) When you are on the ground, make him moving arms and legs to give the impression that he gives an impulsion.

Anyway the making mistakes, i enjoyed the video for the creativity and ideas you bring there.

Good luck for the rest, do not give up, it is a good experience to do.