Reading this, I really felt the experience you had.
It reminded me of what happened to me in 2006.
After 20 years of working for a tiny company where I knew everyone, the owner retired and closed down.
My youngest son had just been born, so I didn't rush to get another job — at least not until I started running out of money a few months later.
Going from a place with 5-10 people, to one with hundreds, was terrifying.
Your decision to sit with the group of students at lunchtime reminded me of something I did there.
After a few months, I still knew hardly anyone. At lunchtime, everyone in my office ate at their desks. The canteen was disused. But I ventured up there and found about 10 people from random departments.
Like you, my anxiety levels were sky-high. And I was terrified of things turning out badly.
But it paid off — I ended up going there every day to chat with them.