Your video has ben removed,, So cant comment there.
Now to your pigeon that is 17 to 20 days old.
Generally, papa pigeon takes over at that age. Mama pigeon stops the feeding.
Looks like you are the papa pigeon substitute.
I think your pigeon is less developed than normal for that age. Should be picking up seeds on his own.
I know you are trying your best, and with the knowledge you have.

If the way you describe pigeon, I thing he should still be getting crop milk substitute. Generally, papa pigeon still feeds Junior until he is about 30 days old. Gets regurgitated seed, which are somewhat softened already. The twice per day you are drop feeding him water,, I think is not frequent enough.