You don’t need to go faster than light. Once you approach anywhere near the speed of light, time slows down so much that journey time becomes irrelevant.
Interstellar space contains neutral hydrogen atoms. Hitting a spaceship, they would produce electromagnetic radiation. When the collision speed goes past about 0.25c, the radiation becomes hard gamma rays which are dangerous to living things, and cannot be efficiently shielded against.
At this speed, the time dilation is slightly above 3%, so you're still not going to reach even Alpha Centauri in one human lifetime, or maybe you barely can.
Right, we are never leaving. We should get comfortable here, and take better care of the only habitable planet, rather than doing insane things and justifying that as "Don't worry, we'll make Mars habitable" and other silliness.
Well, things like the eventual expansion of our own star or the probability of a sizeable asteroid/comet hitting earth tells me, that we should at least keep thinking about leaving. Even if the current tech is nowhere near good enough.
Even if we do leave, it's unlikely that we do so for a very long time so taking care of the planet makes sense even if you intend to discard our crib. Similarly in the nearer term if we had a unified goal to colonize a near planet/moon that's still going to take a huge long term effort to do more than the equivalent of putting a tent up on an island off the coast to get that colony established (if it can ever be self-sufficient).
I think you should assume that the radiation hardened, self healing computer would consider itself alive.
But importantly that's not us leaving. Some distant future descendent of humans could have engineered itself to leave, but it's not us and we shouldn't fixate on that distant and unknowable future.
