Claiming security cheque and gratuity held by employer upon resignation

I joined a Dubai based company as GM in May 2016 and resigned with a one-month notice from 1-05-17 to 31-05-17.

My boss told me to prepare accounts and clear issues ‘AFTER MY RESIGNATION’ (Used these words specifically in a letter) and took a security cheque (Blank dated) with a letter signed to this effect.

Within 37 days I compiled that data with satisfaction on 7-06-2017, and in the presence of auditors, my boss processed my visa cancellation. My boss advised verbally to collect my gratuity and security cheque later on.

After one month of cancellation, my boss filed a complaint in the Labour Department that I joined his competitors whom I started working with them.

Four months after cancellation, he deposited my security cheque in the bank without my knowledge and it was dishonoured. I filed a complaint in Labour, but the matter was referred to the court.

My boss did not recruit a new GM for the last five months, and things got messed up. Now, he is putting all the blame on me for his mismanagement and I am working in a new company now.

I want my security cheque back with my Gratuity. Please advise.