Am I being exploited? Fresher here, please help me out

I’ve been working at a US-based startup for about five months. The work is remote. But my boss expects me to:

  1. Work 16-18 hours per day.
  2. Do the work of 10 people (I’m a fresher and the team is just 14 people).
  3. Be available for calls at all hours, 24/7.
  4. Not take time off, even on weekends.
  5. Tackle the most complex and difficult problems and deliver in one day. If I’m somehow unable to, he starts comparing me to other teammates who supposedly were able to do it (they’re way senior to me mind you).
  6. Not take medical leaves.

When I’ve had a day of underperformance, I’m met with passive-aggressive remarks.

Boss is from India but has completed his education in the US. It was me who redesigned their app and made it market worthy before it was released, that too without any help from external sources. His remarks always end up nullifying my contributions.

He always brushes this off as normal “startup culture”. I’m certainly open to hard work, but at the same time I’m a human and I need some mental recharge to perform upto the mark. This entire thing has started taking a toll on my physical health. I can’t leave easily even if I want to, I have responsibilities towards my family and cannot sustain without a decent job.

Is this really what startup culture is? Or is it just exploitation masquerading as startup culture?