mechanicAL

id be betting on the head gasket, or at least doing a few tests, combustion gas in coolant, cylinder leak test or compression test. low compression in two cylinders next to each other is a good sign the gaskets leaking.

if you can find the sender unit at the tank and test it with a multimeter it may be the problem. or it could be a loose connection. check all the wiring from tank to dash. note the colour at the tank and follow it. checkng for breaks or bad connections.

the misfire could be due to a bad coil do a power balance test by unplugging each coil one by one, note engine lower in power. pay attention to cylinder 3 .... Do you know how to do a coil test/ spark test... take out the coil and connect a spark tester. turn ignition. look for spark, or use a screw driver. the fuel trim being rich may be due to a blocked air filter.... if not that simple try looking at the fuel pressure regulator on the fuel rail, there should be a vacuum line attached, check for fuel in the line, if there is fuel in there the fuel regulator is leaking and needs replacing.

have a look at fuel trim on your diagnostic live data if you can... any double figures i.e 15.50 +or- could indicate a vacuum leak.

does it idle badly?

get a multi meter and test the battery for 12.6 volts, voltage should be no less than 12.4 really. the starter motor runs striaght off the battery and need a fair amount of current to function. do a crank test too, disable ignition and crank the engine while the multimeter is on the battery .. shouldnt fall below 9v.