I know the P0300 and P0304 are random cylinder misfire and cylinder #4 misfire,
not sure about the others, but,
a good place to start, would be changing your plugs and swapping your #four coil with another and see if the misfire follows that coil.

 

The good news is these AJ-16 straight-six engines are bullet-proof, but sadly the bits that surround them are not ! One of the failure points is the plug coil over each plug. In the UK these are known as a regular failure item. Other things that fail are the crank position sensor, and the camshaft position sensor.

I assume by "alt. needle" you mean the volt meter on the dash. This could indicate the alternator is on the way out, but suggest you check voltage at the battery +ve terminal both engine stopped, and engine running. There should be around 2 volts difference.

I cannot translate the fault codes, you need someone more expert than me.

 

you should be getting just at 12 volts or right below with engine off,
and about 13.5 volts with engine on.