Server audit with more than 1.000 entries
Have you tried reading your audit using sys.fn_get_audit_file?

-- query all audit files in the D:\audit directory
SELECT *
 FROM sys.fn_get_audit_file('D:\audit\*.sqlaudit', default, default)


The CREATE SERVER audit TSQL command you used did not specify 

MAXSIZE = { max_size }
The default value is UNLIMITED.

MAX_ROLLOVER_FILES ={ integer | UNLIMITED}
The default value is UNLIMITED. 

MAX_FILES =integer
Specifies the maximum number of audit files that can be created. Does not rollover to the first file when the limit is reached. When the MAX_FILES limit is reached, any action that causes additional audit events to be generated will fail with an error.

Not sure what the default is for MAX_FILES but its probably the FS limit which is somewhere around two billion.

So no there should not be any limit on the size of the audit files generated or the number of rows stored within them.