he lowered toehold rpm and consequently yes it would cause less jerk but thats a solution only if idle rpm in the first place was not royal, it would be around 800-900 in idle and 700 in D, whats the idle rpm now?
and since the car is EFI theres a good chance that whatever adjustment the mechanic did with that screw would be cancelled by the ecu in a little while,
keep reporting updates
and what is going to do by servicing the throttle body? don't let him dunk it in petrol just use a carburettor cleaner spray, spray it on a rag and use that to clean it, don't even clean directly, it will create more problems later