What are the limits of Postgresql's large object facility?
These 3 points are correct. We might add


A large object cannot exceed 4TB for PostgreSQL 9.3 or newer, or 2GB for older versions. This is based on the release notes:



  E.11.3.5. Data Types
  
  Increase the maximum size of large objects from 2GB to 4TB (Nozomi Anzai, Yugo Nagata)




Also, the binary contents are sliced into tiny chunks of 2000 bytes in pg_largeobject. There is one row per chunk, so when importing large contents (large by today's standards), the number of rows in this table tend to grow quickly.
Although that does not imply a hard limit, users should be aware of that for performance reasons.