No you havent caused any problems or bad feelings, opinions vary and hopefully result in good discussions and hopefully lead to fixing your car as well as mine, by the way adding diesel fuel treatment for bug will not harm your engine, its no different to adding redex or something similar to clean your fuel system/injectors.

As your filter change did not fix your problem which is the same as me then you will need to be looking further into your problem as Dan W has suggested, your mechanic will need to access the stored codes within the ecu, an obd2 reader will only read generic codes not the hidden ford ones (if there are any stored) which will be more usefull in diagnosing the problem.

From what you describe it does sound like a fuelling issue (pump/injectors/metering valve/possible restriction in the fuel delivery pipe) or it could be a turbo boost problem (split hose etc) but without seeing stored codes or viewing live data when the engine is running or trying to start, you wont really know where to start looking first.