Engine misfire? I've been getting the P0301 code?

That's because you disconnected the battery. The Engine Computer has to relearn "minimum throttle" before it will know when to be in control of idle speed.

To meet the conditions for the relearn to take place, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.

Engine misfires can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.

I think that is a good idea. Let me know what you find.

You never want more than a 10% variation between cylinders. Based on the coolant issue, my guess is you have a bad head gasket.

Check wiring or clean/replace the CMP/CKP

Camshaft Position (CMP) sensor is located on rear of cylinder head, just below valve cover. CMP sensor uses a target magnet attached to rear of camshaft and uses locating dowels for proper positioning.
As target magnet rotates, CMP sensor senses the change in the polarity. The polarity change causes CMP sensor output voltage to switch from high-voltage of 5 volts (at magnet north pole) to a low-voltage of.3 volt (at magnet south pole). CMP sensor delivers input signal to Powertrain Control Module (PCM). PCM uses this input signal along with input signal from Crankshaft Position (CKP) sensor for determining crankshaft position for fuel injection synchronization and cylinder identification.

Camshaft Position Sensor (3.3L & 3.8L)
Camshaft Position (CMP) sensor is located on top of timing chain cover, just below thermostat housing. End of CMP sensor is located directly above camshaft sprocket. A notched ring is mounted on front of camshaft sprocket.
As camshaft rotates, CMP sensor generates pulses due to notch areas on the notched ring. When solid metal area on notched ring passes below CMP sensor, voltage decreases to less than.5 volt. When notch on notched ring aligns with bottom of CMP sensor, voltage increases to 5 volts. Switching of the voltage generates pulses. These pulses provide an input signal to Powertrain Control Module (PCM). PCM uses input signal along with Crankshaft Position (CKP) sensor input signal for determining fuel injection synchronization and cylinder identification.

Crankshaft Position Sensor (2.4L)
Crankshaft Position (CKP) sensor is located on cylinder block, behind generator, near oil filter. Crankshaft contains a crankshaft pulse ring which contains 2 sets of notches ground into the No. 2 counterweight.
As crankshaft rotates, CKP sensor generates pulses due to notch areas on the No. 2 counterweight. When solid area on crankshaft pulse ring aligns with bottom of CKP sensor, voltage decreases to less than.3 volt.
When notch area on crankshaft ring aligns with bottom of CKP sensor, voltage increases to 5 volts. Switching of the voltage generates pulses. These pulses provide an input signal to the Powertrain Control Module (PCM). PCM uses input signal to determine crankshaft position. PCM uses input signal along with other various input signals for controlling fuel injection synchronization and ignition system.

Crankshaft Position Sensor (3.3L & 3.8L)
Crankshaft Position (CKP) sensor is located on top of transaxle housing, above flywheel, near corner of rear exhaust manifold.
Flywheel contains 3 sets of slots areas near starter ring. Each slot area contains 4 slots in each set. As crankshaft rotates, CKP sensor generates pulses due to slot areas on the flywheel.
When solid area on flywheel aligns with bottom of CKP sensor, voltage decreases to less than.3 volt. When slot area on flywheel aligns with bottom of CKP sensor, voltage increases to 5 volts. Switching of the voltage generates pulses. These pulses provide an input signal to the Powertrain Control Module (PCM). PCM uses input signal to determine crankshaft position. PCM uses input signal along with other various input signals for controlling fuel injection synchronization and ignition system.

I would pull the spark plugs to see if one is fouling out from a rich condition. A bad o2 could cause the fuel system to be driven rich all the time, it should show a fault code.

Go to this link for further info:
https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Hav eit scanned for codes and check fuel pressure with a gauge then have a pro check coils/plug wires etc.

I'm not sure I understand. You have a misfire, no check engine light, and you replaced the plugs and wires and nothing has changed? Have you checked to make sure the injector is firing? Are you getting spark to the bad cylender? Have you checked compression in that cylender? Fuel pressure?