Why wont my car start after removing & reinserting the battery fuse relay?

Sound more like a worn out battery to me. Have you had it load tested? If its 5 years old or older just go ahead and replace it and see what happens. They don't last forever and can cause all sorts of problems if they are not up to full strength.

 Ive changed the battery & the fuel pump because there was no fuel pressure, there's pressure now but it's still only cranking & not turning over. It did turn over for a second when I sprayed staring fluid into the throttle body. Does it sound like a starter issue?

No, not at all. The starter doesn’t start the car, it just spins the engine so it can start...if that makes sense. If the engine turns when you turn the key the starter is fine. Sounds like fuel is somehow not getting to the spark plugs. No power to the injectors maybe?