Dear Young-man-at-a-loss,
Returning the company laptop
What is not yours, is not yours. I am referring to the laptop. Whether an agreement is arrived at or not, it must be returned.
Outstanding payments and legal considerations
As far as the outstanding payment(s) is/are concerned, there are many issues to be looked into: did you, during your employment stint, have the company's coverage for the days you were off - and what amount receivable actually accrues for you. Since you don't appear to have a written official contract, you will need some legal intervention to receive the payment.
Legal advice and career implications
You are walking a tightrope, and since it's your professional career in infancy, DON'T DO ANYTHING CONTRARY TO LAW. Seek legal advice; if you don't, the employer may lodge an FIR against you, and that would breed ill on your future CVs and prospective employers.
Maintaining ethical standards
Rationalize the situation, and prove you go by the highest standards of ethics in all situations, a trait often needed in professional institutions.
Learning from the situation
The silver lining, from the issues you created for yourself, is the lesson you learn from it. Have a positive attitude towards the entire scenario, and see how the attitude will help you wade through similar storms in the future.
Regards,
Arif ur Rehman