Can't start 1997 Mounty 5.0

[Pineapple King]

Had this Mercury Mountaineer V8 1997 for 3 years, no issues, hardly had to do any repairs.
I have no experience with repairs but an averagely gifted brain to fix this issue.
What I could really use is some advice though, as I'm puzzled by this no start condition.

Without any warning, the car would not start anymore. Could get it to run 3 times since, but it's a 1 in 10 chance and most days it refuses to start at all. Could not pin it down to weather,cold temps, or anything.

It cranks just fine. After trying to start it for a while, sometimes it comes on, it runs fine, drives great. Acceleration is good, no rough idle or anything. Will not start up again after drive.
I noticed it had a hickup/miss in idle once or twice the week before the breakdown. Nothing else.

The car had these codes for the last 3 years:
- p0141 O2 Post cat sensor down
- P0443 Evaporative Emission Control System Purge Control Valve Circuit
I assumed both have no negative impact on day to day car operation but they throw the check engine light

Recent repairs done before breakdown:
- New Camshaft Synchronizer incl Sensor, installed at home. Used cam sync tool and everything went fine. 500 miles since new camshaft synchronizer.
- Tried to recondition low battery. Around 11.6-12.2V at the moment. Battery might be bad.

Symptoms:
Key position "On"
- Check engine light comes on, as it always did. No connection to ODB2 tool at this stage, can only read codes when running? No new codes in system anyway
- Theft lamp does not flash
- Fuel Pump runs permanently. As of today, after investigating the fuel pump relay, the fuel pump will not come on anymore, except when jumped.
Key position "Start"
- Cranks, but no start.

Diagnose/Repair after breakdown:
- Replaced Camshaft Position Sensor with old one.
- Reconnected Camshaft Sensor connector a few times
- Diagnosed Power Distribution Box, all fuses fine
- Cleaned Battery Poles and tried to jump start with a second car. Cranks vividly but no start
- Fuel Relay is a mystery to me. At first, the fuel pump was always on with Key in ON position. Now the fuel pump / fuel pump relay stopped working at all. I get the permanent on signal with the multimeter in the power distribution box, but the relay does nothing. Switched the relay out with AC and EEC relay, nothing. Jumping the fuel relay turns on the pump, but still no start.
I doubt all my relays are bad? Whats going on here.
- Went through forum no start guide with no conclusive idea on what's wrong yet

Now I'm left with a bunch of odd issues that I can't really fix myself.

1) Who's the culprit with the no-start condition?
2) Should I be worried by the fact that my fuel pump is permanently on with Key in ON position?
3) Why is the fuel pump relay not switching anymore?

My best guess so far is, maybe fuel pump/filter issue plus I seem to have busted something about the fuel pump relay or the slot it sits in during the process of playing around there.
Any ideas on how to proceed with diagnosing from here? Do I have two issues (Fuel pump plus fuel pump relay) or is this one issue that shows in ways I do not understand?

I will post my results from the no-start checklist in post 2

Thank you for reading and your help in advance!

 

[Pineapple King]

Started working on "no start" checklist, can't pin it down yet.

1. Turn Ignition Switch to On
Does "CHECK ENGINE" illuminate?
Yes:

2. Do you hear the Fuel Pump run for a few seconds when Ignition Switch is switched to On?

Ran permanent until today. Stopped running at all now but will power up when fuel relay is jumped.
EEC relay clicks when key is ON, fuel relay does not.
Signal to fuel relay is fine but permanently on with Key to ON
Rotated all Relays, no change.
Car does not start with jumped fuel pump relay.

3. Does fuel pump should run continuously when jumped?
Yes: Failure is due to fuel pump relay or PCM control of relay. Go to step 9.

4. Is Inertia Fuel Shutoff (IFS) switch set (button pushed in)?
Yes

5. Is Fuse 9 (20 amps) in the Battery Junction Box good?
Every fuse tested and good

6. Disconnect Fuel Pump/Sending Unit electrical connector (C311) located on the inside of the left frame rail in front of Fuel Tank.
7. Is the resistance from female C311, Pin 7 (black wire) to ground less than 1 ohm?
8. Is the voltage at female C311, Pin 6 (pink/black wire) battery voltage when Ignition Switch is switched to ON?
6-8 skipped

9. Remove jumper and Swap Fuel Pump Relay in the Battery Junction Box with the Rear Wiper Down Relay in the Battery Junction Box and repeat step 2 above.
Started the pump but not the car

10. Make sure PCM connector bolt is snug (do not overtighten).
11. Remove PCM connector and see if pin 80 is pushed back.
10-11 skipped

 

[Pineapple King]

I went and confirmed that all relays are functional. They are. I'm puzzled.

The pump runs when the fuel pump relay is jumped.
The relay works outside the car hooked up to a battery.
The relay slot in the power distribution box works, too.

Putting it all together, the pump won't turn on.

I would like to eliminate the rela from my list of issues that keep the car from starting, but no luck so far. Any input appreciated