Hey, thanks for the message! I did get your email, and responded to it already :)
Here's what I'd sent in case you didn't get it:
Thanks for reaching out! This looks like a very cool project, I'll be excited to see what you do with it.
Yes, you can absolutely use music from the The Monolith. I would just ask to have my name and website credited like you mentioned.
Also if you're ever interested in a custom soundtrack for the game in the future, let me know! It would be fun to work together.
Cheers and best of luck,
- Major