Tenant did not honour the rent agreement

I am a landlord. i gave my flat on rent. As per rent agreement he has to maintain and keep my flat in an good condition and to comply with rent agreement clauses but he ruined my flat and he did not serve any notice before vacating . I recovered damages from the security deposit which he deposited(for painting, plumbing and cleaning..etc). But now he asked me to return security deposit and sent me a letter mentioning that normal wear and tear does not come under security deposit and threatening me to refund security deposit otherwise he will take legal action. He violated many clauses of the rent agreement such as: 1) He did not serve written 30 days notice prior to vacating flat. 2) He ruined/dilapidated my flat.(i have pics) 3) Rent was not paid on time. As a good gesture and humanitarian ground we did not take action. But now learnt he is taking undue advantage of this. Please advice and course of action have to recover my losses from him and where to address.