I rescued this little guy around 3 weeks ago. I never took care of a kitten before, but fortunately he's been making amazing progress. He's almost fully weaned at this point.
Shoutout to user Joshua Nozzi from my previous post, who urged me to see a vet. If I went any later he may wouldn't have made it.
Thanks again mate. When I brought him to the vet it turned out that he was severely constipated. After the vet relieved him and a few days of kitten formula he seemed like a completely new cat!