If you are keeping the same Houskeeping and only adding a page, leave the backend as it is and design the page using HTML/CSS, obviously make sure the "new" page is in the same folder as the other files and be sure to link it correctly.
And you followed everything correctly? ports are open and what not. I'd trace back and go over everything again. Check everything for the sake of it, config also.
If you're referring to your client not getting past 20%, open up the console and check which errors it throws.
As well as that, be sure to verify everything is it linked as it should be.
You're right, do follow Object's tutorial. It's straightforward. If you take your time working through each step you'll succeed with ease. Another advantage to this is any troubleshooting you need to do, the answers are pretty much all within the comments!
I think you misread. First, I did not say you were advertising; I said be sure not to advertise anything Minecraft-related on retro platforms, even accidentally. I also never said "Moderation" was an exclusive term for Habbo Retros. Of course, "moderating" differs depending on the game for many...
Listing previous experience, what you bring to the hotel and so on will probably help you a little more.
In my opinion, Minecraft whether you're playing on someone else's server or your own won't matter as it's nothing related to retros, obviously just don't advertise anything Minecraft...