First of all, amphetamines are NOT an answer. Drugs, no sleep, etc, are just setting you up for a major, ugly crash.

I know it's a problem, and drug abuse has been an issue for me since I was 15, but I just don't have the time or resources to tackle it right now. There's so much work that has to be done (that I want to get done), and the only way at the moment for me to do it all is to use drugs. Stopping now would cause a crash, and I can't even take a weekend off let alone the 3-4 weeks it'd take to withdraw from some of the heavier stuff.

Second, you need to take ownership of your work and your time.

I do tell him when I have too much work and I try to provide more realistic estimates of when I can get certain work done, but I feel obliged to work hard, like I want to make a really good impression. The PI might say "Make sure you don't overwork yourself", "Make sure you're getting enough sleep", etc. but I still know that he wants it done yesterday. I don't know how he does it, he's just so nice and innocent about it all that everyone gets sucked into a mindset where they have to drop everything to get his work done.

It's like everyone gets hypnotised during team meetings and then we all agree to take on way more work that we can handle. Even when you prepare yourself beforehand to turn down anything extra, you still do it. I don't think the PI's insistence on maintaining hierarchy helps this.