1. It's good, go ahead! Just be careful if you are using assets made by people outside the team, as their use hinges on them authorizing it.
2. I think he likes his own Texan accent and makes an effort to keep it.
3. He looks like a sort of Doom-esque demon. His skin has that magmatic-esque texture to it. He has internal genitalia that comes out when he's aroused.
4. Kota's update hints at this just a tiny bit, but it's best not to assume a mythical's age by their appearance or size! The cobalts look tiny and act in very silly, childish ways because that's just their nature, but in truth they can live very long lives (in Minotaur Hotel-verse. Their fate may be much shorter in other settings.) Don't be surprised if the goofy little cobalts are much, much older than they seem like.
5. As a rule of thumb, if the mod has no issues like copyright infringement, illegal content, malware, does nothing ethically shady, then we'll probably be alright with people accepting tips on their pages. On principle I quite enjoy the idea of honest modders getting tips, and in fact I've explicitly told a few of them that it's alright and perhaps they should do it. But we'll hold the right to reject this, if we deem there's something possibly negative or harmful going on.
Another way to put it is that if it's made with love and respect, it should be good. For all of the mods/fan games currently on our collection we would have no issue at all if they accepted tips. But if a modder wants to know for sure you can just contact us wherever is most convenient for you and ask.
6. The license does not cover fan works. Sadly. Neither does it cover people posting on Youtube via Let's Plays, which IMO is one of the main flaws with the service we used.
However, if you are working on a MOD that PATCHED on top of the base game, you are not distributing the songs. You'll be in a good legal position. That is to say that if you are making a mod that's put on top of Minotaur Hotel, you can use the songs that are already in the game with no issue.