<p>How safe do you think it is to run an SLA 3D printer in the bedroom? I am planning to run Mi Air Purifier 3H/C while the printer is running, I am also thinking about adding <a href="https://rads.stackoverflow.com/amzn/click/com/B086277CNQ" rel="nofollow noreferrer" rel="nofollow noreferrer">this</a> inside the actual printer (Elegoo Mini Air Purifier with carbon filter).</p>
<p>Is this safe or still too risky?</p>

The motor is mounted in a fixed position no matter if it's on top or bottom.
You can imagine the lead screw as a rod hanging down and supporting the bed in the Z direction only, because all of the XY rigidity comes from the Liner rails the bed is attached to it works just as well if the stiff rod is under compression instead of hanging from the rod.
Any forces that might "pull it straight" are the same forces that can cause Z wobble so you would not want to even try to use the misalignment to straighten a bent lead screw.
The only thing this that really changes with this orientation is if the lead screw is under tension or compression. Even a relatively thin lead screw can easy counter the forces of gravity and the forces is the same in both directions. Its easy and cheap to make a smooth rod or rail straight but not so easy to make a threaded one straight.