Is it permissible to take the remaining 65 Egyptian Pounds from the governmental travel allowance, given that recording the actual due amount is rejected by the administration?

If the amount disbursed for transportation from government offices is not exaggerated, then the difference between it and what you spent belongs to you. However, if it is exaggerated, you must inform the responsible authority, unless you fear harm. In that case, spend the difference on the interests of Muslims, such as the poor, the needy, and hospitals. Do not spend it on building mosques, to avoid disagreement.