I was in the exact same situation as you and feeling just absolutely depressed and miserable since accepting the PIP — you feel like everyone else is handling it, but somehow why can’t you?! I just want to tell you that you’re absolutely not alone, and don’t feel guilty to do what is right for your mental health.
As for interviews, I can only offer my two cents — I tried to think of the accomplishments and projects I’ve worked on, and despite the toxic culture we currently have, we have touched some impactful projects in some way, even if it’s a small contribution in a mega project. Your interviewer will likely be very impressed by the kind of projects you contributed to, and that’s something to be proud of! Not everyone in the world gets to work on international assets with millions of investments in just absurd locations on the earth. Be proud of yourself for having a part in it, and I hope that gives you some confidence in these interviews. Best of luck to you, keep chasing what you want, and this is just the beginning of what you know you need to do to make yourself happier! I know you can do it!