Wasf, you cant complain of radiator water level drop at any given time just by 100ml drop which I guess is 1cm drop visible through radiator cap area, if your tsat valve is working. This is the job of tsat valve to regulate water between engine block and radiator. You should post a pic of what you are referring to as water level drop. Change your Tsat valve with a new qabli one to remove doubt.
Radiator fan activates through thermostat switch which is disabled when direct fan is applied by your mechanic. One mistake leads to other. Better get your wiring upgraded. This is no joke. It should work like it is designed.
AC tripping after 15 seconds is not right either a high gas charge is causing it or your AC guy has tuned it to prevent heating the compressor. Get your AC tuned again.