No start no crank 04 ford explorer?

When i put the key in the ignition switch the lights come on but it only makes a clicking sound, nothing else.

I went through the simple tests:
1)My battery is good
2) i checked all my fuses and relays
3) we took out our starter and it tested good
4) since we had a oil leak from valve cover gasket i changed the spark plugs

I have two theories
1) the fuel pump is bad
2) the engine locked up

1) i did the gas cap hearing test to see if it makes a sound when you turn on the key but i didn't hear anything, if i did it was just a faint sound that can barely be heard

2)it does have oil but when i try to turn the harmonic balancer/ crankshaft pulley it won't budge, i'm using a regular ratchet because i don't have a torque wrench but does it matter? I'm turning it clockwise, unless its supposed to be super tight cause it won't budge

any suggestions or other tests i can do

Added (1). We took the starter off and went to a parts store to test it since i suspected it might have gone bad from all the oil leaking on it from the bad valve cover gasket but it tested out good

It does have anti theft but i don't know how to mess with it or diagnose to try to help my car

Clicking is solenoid trying to engage motor in starter. Often a result of low power ( flat battery) .corroded or loose connections, solenoid fault etc it can fail to crank over.
if we're sure starter is good ( did we try a jump start?) then your other description of being unable to turn crank over by hand is worrying. With plugs removed we ought tone able to crank it over. Not always easy without a long turning bar! By hand.
if it is locked solid? Then starter will click and not crank as motor can't get past the torque needed to start cranking.
is engine in fact seized? Fuel pump won't affect cranking. Anti theft device will! Is anti theft 'off'? Check if crank turns by hand? Then have antitheft ( sometimes referred to with other names e.g. Ford 'Pats" system )

The fuel pump has absolutely nothing to do with cranking an engine so you can eliminate that. Get a heavy cable and jumper the start solenoid. If it cranks replace the solenoid. If it doesn't then you may be right about the engine being locked up.

Take the serpentine belt off then get a bigger ratchett and try to turn the crank clockwise. If it doesn't move? Its junk. And if its 4.0 single overhead cam junk it definitely.

Check the starter relay on the fenderwell. Make sure it is grounded well. Clean any signs of corrosion as it grounds thru the fenderwell. You can jump the relay/solenoid, and get juice down to the starter, by placing a screwdriver across the positive battery cable end and the small post on that relay.