How do i politely distance myself from someone?

Recently i’ve gotten closer to a friend, but he’s basically told me that he’s starting to like me. He has a lot going on so i don’t want to be harsh. But i don’t see the purpose of dating if i can’t see myself having a future with someone. I’ve also seen the way he react to breakups, and it’s quite toxic. I’ve started to reply slower, and i feel like all of the replies i’m getting are vaguely manipulative? I’ve asked my sister about it and she thinks the replies are as well. And if i don’t call or hang out it’s always ‘oh okay’ etc, and idk how to feel

Another important thing to mention, while we’re close in age. They’re also a manager at my workplace, and i fear it becoming stressful for me

I want to stay friends with him, but i feel pressured to reply quickly or call when i don’t feel like it, because he’s always saying he plans to kill himself.

advice?