Stop throwing parts at the problem, this is a very simple system, perhaps get a new mechanic

Check the distributor pickup by using an ohm meter across the connector.
I do not remember what it is supposed to read but it is simple ohms.
when the distributor spins you can see the meter read the reluctor - the meter will show continuity then an open circuit as it spins
This is known problem that over the last 10 years has crept in due to lack of quality in the parts