Should I invest the time to change the column type from CHAR(36) to UUID?
I would consider changing to the UUID type.  char(36) takes 40 bytes, uuid takes 16, so you'll save 24 bytes per row, which for you will equate to 12 MB a day, 4 GB after a year.  Plus indexes.  Depending on what hardware you have, that isn't much, but it could be.  And it adds up if you have more improvement opportunities like this.

Also, I see no constraint in you schema that ensures that interaction_id is actually in the right format.  Using the right type will give you that as well.

If you like this, however, than using bigint would save even more and have even better performance.  It's very unlikely that your application is so large that a bigint for an ID column won't work.