1. if your salary is not more than RM2000, the 30 days maternity leave is not valid. It should be 60 days with pay. If your salary is more than 2K, then you are not covered by the EA. That clause of 30 days may be valid.
2. Non disclosure agreement clause is not provided in the EA.
3. Up to the company to decide how to calculate.
4. That's is not good. Get them to put in company's name or company chop.
If you are faced with too many problems with the company, you should bring them up with the Labour Department.