So I don't know if this has been pointed out, but no product placement? Really? Have you ever heard of Gibson, a huge manufacturer of guitars based out of Nashville? Nearly every famous guitarist that has ever produced music has used Gibson. It's a household name, and not only is the brand all over the show, but the logo is HUGE and shown at the end of every episode. It's a bit ignorant to miss such a huge corporation being marketed.
As far as the show being appropriate, let's think about this. It's on a program called ADULT SWIM at 12:30 at night. I don't think many children will be watching it. And I believe it is acceptable for people, at the very least, 15 years old and up to watch. As far as all the violence, swearing, drinking, and such, this is a show that is parodying heavy metal bands in a way that is designed not to make fun of them, but to be funny and joke around about the music industry. It's not to be taken literally, but for what it is: A funny show for metal fans.
Also, just a side note. They didn't put the chef back together to write a song about him. They did so because they were hungry. And wanted a sandwich. It's obvious you did not watch more than the first episode.