Would rendering stuff (max temp) while the screen is closed cause the screen to break?

If closing the screen is causing water vapour to form or other odd issues then stop doing that. Water and electronics don't play well together. Since you've already experienced some issues I'd suggest you have your mac inspected at either an Apple Authorized Service Provider or an Apple Store in your region.

Hello there,

You should avoid having water on your Mac, but having the screen closed, even with handprints on it, while you're rendering shouldn't destroy the screen. Lots of people use MacBook Pro laptops connected to external monitors with the lid closed for rendering work.

Nope, you should be good! Just treat it nice and enjoy it, and it will last you a long time.

Nah, I don't think you need to be worried. They're built pretty solid. My personal guess, but it might be just because you leave it closed a lot? No need to apologize. It's what we're here for.

You’re welcome!