Understandable. There isn't a ton of information out there for them. The melleri discovery is a good source.
One thing you want to remember is that they do not like constant humidity like most montanes. They actually like spikes in humidity and then for it to drastically drop. I give my melleri 45 minute drinking sessions in the morning. Then I let them dry out all day until their evening shower. This will be more pertinent as your guy grows. Right now as a sub adult and fresh import, I think it is good to keep his humidity up until he fully rehydrates. His eyes will become much fuller actually.
I am super happy to hear that you are tracking his weight....well done. That is so important and a step that most leave out. So kudos. Once he acclimates in about 3 months, make sure and have a fecal done. Don't treat for any parasites right now, as they are prone to crash with mass die off.
How is his appetite?