Why does simple ALTER TABLE command take so long on table with full-text index?
The schema change it taking so long because you are assigning a default value to the column during the change and enforcing that with a non-nullable column, and it has to populate the column for 60+ million rows, which is an incredibly expensive operation.  I'm not sure what your application requirements are but an approach that would make the schema change faster is to add it in as a nullable column with no default value and then perform an update in batches to assign 0 as the value for the column.  After your update are done then you can apply another schema change to change the column to non-nullable and assign the default value.