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Hello, let me rephrase and summarize first... we can split the hairs later.
The component tests will show that they are working properly even if the humidity is way high.... so the issue is NOT if the components are bad.... this is a matter of adjustment is all, very simple adjustments that most HVAC contractors are quite familiar with... your dealer is apparently not in that class.
Judging by his ill formed attitude it may be a waste of time to talk to him... but you could try.
Tell him that this is a matter of air flow across the cooling coil and that the established solution is to slow the air flow down so that the cooling coil runs cooler and takes more humidity out of the air.
The above is true IF and only IF he has not over charged the system with refrigerant.... nor grossly over-sized the system.
This is step one in getting your situation resolved, I will stay with you on this until the problem is solved.