Yes. This is a word search.

No.

When a number is in a circle, what does it normally mean in the book?

A number with a line. A line number.

Don't just look at the line. Look at the whole paragraph.

When you look at the line-art on the door, what do you see? It shows you how to find things.

In the epigraph, it says "The third’s instructions also contains your goals."

Everything you need to find is given in the inscription.

Start with the line "Seek | 51, 5" That's the easiest one.