It's not even a week yet and he looks like a new kitten.
His eyes are clear, he has no snot. The bald patch near his mouth is tsill there but it's not crusty anymore.
He eats about a 3rd of his bodyweight everyday and he's become very playful in a rather psycho way.
He even uses his litter box if he's close enough when the urge hits.

Fingers crossed he keeps on keeping on.

In a few days I might introduce him to my cat and see if they get on because I think he needs some guidance from an older cat.