Are expdp/impdp commands appropriate for daily schema sync?
No, that is not a possible way:  


Most of the non-table objects will already exist in your schema. You already get such error messages. The import will not overwrite it.    
You can configure how export should work if a table already exists but if there is a table that s referenced by another table then TRUNCATE and REPLACE will not  work.
Even if there is no foreign key reference to a table indexes will slow down the import dramatically
A lot of other problems may occur (concerning triggers, partitions, references to other tables and maybe more)


So the only reasonable way to synchronize the schema using expdp/impdp is to drop the schema before you import.

If you don't want to drop the schema for some reason but replace the data of the tables  a lot of additional operations are necessary.