No, not possible with DB Replacer. You can only search and replace in 1 table at a time.
To do replaces in multiple tables you will have to repeat the replace process for each table.
Another method is to execute your own custom sql command on your database directly, via phpMyAdmin for instance.
You can match empty, NULL or 0000-00-00 date values by simply placing
NULL in the search area.
You can match the entire value of a field by placing a single asterisk
* in the search area.
For more info on Regular Expressions: http://www.regular-expressions.info/reference.html
For testing them: http://gskinner.com/RegExr, http://regexpal.com, http://www.phpliveregex.com