The Dubai shop suspecting refrigerant on a fault that works perfectly at speed is not a strong diagnosis. Low refrigerant causes consistent weak cooling, not a speed dependent pattern that disappears on the highway.
550 dirhams against a significant front end collision repair on a 95,000 dirham SUV is the clearest possible return on investment in used car buying. That inspector earned every dirham of that fee.
165k kilometers on an E350 that you want to keep two more years makes a proper transmission diagnosis essential right now. A whining pump ignored for a few more months usually becomes a full rebuild situation.