Based on my own experience and memories, I think using free will to harm someone can't prevent them from gaining the life benefit they're after. It's a bit like blocking a goal in a soccer game. There's always another chance and if there isn't enough time this time around, there's always the next game. When we're unconscious of the greater span of time, it feels like this is a one-time-only event, but in the larger view we all figure things out one way or another.
From what I've heard many actually plan lives around experiencing the worst that human life has to offer, even knowing it will be a miserable experience. Maybe we see smaller hints at the reasons why in people who enjoy the horror genre or extreme sports. There's something to be gained by facing true hardship, and (again, in the larger view) we tend to feel it's worth it.
I know that's my own experience. I wouldn't exchange the years I spent being abused now that they've happened, even though I can't imagine volunteering for that again, because I'm grateful for transforming into who I am now and all I learned through the pain. The people who treated me that way still are that kind of person as far as I can tell, but I've become someone capable of seeing how fearful and trapped they are due to their mindset. I'm capable of holding boundaries that keep them at a distance or avoiding them entirely.
From what I can tell from the memories of a life I ended early, I simply learned from the information gained in the process (Basically, oops ... I could have had this whole amazing life if I'd stayed. That was a mistake. Next time I'll choose to live anyway. And I did live this time, surprising myself.) In between, I had various difficult lives where I learned to face the attitudes that had driven me to end things and instead grow through them and learn to survive.
Along the way I learned not to try to control others, even when their free will harms people, because it just slows down both my own and their growth. Often trying to fix or help people leads to intrusive and controlling behavior, even when we think we're being helpful because they're being hurt or hurting others constantly.
The downside of free will is that people only learn when they're ready. Because of this, one of the more useful life skills is learning to identify who is ready, how much support or advice they need, and when to step back and let them experience pain so they can learn from it.
So, yes. Everyone's free will influences everyone else's lives. Human life is constructed to function that way. We're capable of handling those seemingly unexpected shifts in our plans, sometimes to the extent that (looking back) it feels like we might even have planned to face that particular challenge. Some do remember planning such things.
Suicide isn't a solution. The inner growth gap of each soul tends to make room for pain. Those gaps remain open for exploitation in other lives until experience helps each of us become capable of surviving and even valuing it as a growth experience. It sounds unfair. And being treated so badly IS unfair. It's not right or acceptable or moral. And it is still possible to become someone who is resilient and refined by those experiences rather than destroyed. We only learn that by living through it until we figure it out, and that can take time.
However, there are many different growth paths and lessons to learn along the way. Not everyone will have the same experiences when it comes to dropping out of the game early. Still, the one element that nearly everyone (with such a memory) has mentioned is regret for the potential gifts they lost and the harm they caused by leaving.