Does the claimant have the right to dispose of a sum of money recovered for his company after resorting to "devious methods involving suspicions" to end the dispute? Is he obliged to inform the employer of the details of the agreements that were later canceled? Is he required to return all or part of the sum, and when?

Your legal work for the company is a private ijara (lease/hire contract), and as a private employee, you are obligated to safeguard the trust (amanah) and perform the duty for which you are paid. Therefore, you have no claim (or favor to bestow) in recovering the company's debts. What you spent of money, with the permission of the company owner, on the lawyer and others for the purpose of recovering the debt, there is no problem with that. However, your taking a portion of the amount allocated for this purpose is impermissible for you, and you must return the remainder to the company. There is no need to inform its owner of the details if that would result in harm, unless he explicitly permits you to keep the remaining amount.