Rough idle, missfire, insuficiente EGR flow

I am having problems with multiple codes and need help finding a solution. I have a cylinder 1 missfire code, multiple cylinder missfire code, insufficient EGR flow. It runs rough on idle, missfires and is now leaking coolant. I have replaced spark plugs, coils, wires, egr valve, egr manifold, egr gaskets, intake gaskets, throttle body gasket, multiple hoses, fuel pump, fuel filter, and radiator cap. I had code p0402 (egr valve stuck open- to much flow) but after replacing egr manifold and valve I have p0401 (insufficient egr flow) coolant just started leaking and oil is clean and not milky but I am replacing head gasket anyways. Also replacing o2 sensor soon. Code p0300 and p0301 are the missfire codes. The injectors are good but don’t know what to do next. If I can’t fix it I might sell it but I would rather get it running good again and pass it down to my son one day.