Employer's request to sign a clearance letter for unpaid dues upon termination

I was a Project Manager for a company. After 9 years of my service, the company has terminated my services for the last 45 days (Because work is less & they want to downsize the staff strength).

I don't mind going back to my country, but they are expecting me to sign an Arabic letter stating that all my dues are paid, for the closure of my visa which is getting over on 07.10.2017.

Since the financial condition of the company is not good, they are not in a position to settle my gratuity & other benefits. They are not giving any clear-cut date on which they will settle my dues.

My worry is that once I sign the Arabic letter & my visa is cancelled, I cannot continue in the UAE beyond 28 days after visa cancellation.

I don't want to go against the company to pursue legal step, but at the same time, I am worried about my dues that I may be denied once I sign the Arabic letter & I am out of the UAE.

Please advise what I have to do?