Your pressure should be ~42-45 PSI as soon as you turn the key to position 2 and then to 50+ PSI once you turn the key to start.
After the car sits for a few days it will be 0 PSI. The spec for holding fuel pressure is after 20 min the pressure shouldn't drop more that 7 PSI (from 50+).
Change your fuel filter, if the pressure doesn't return to normal your pump in probably shot.
Check for spark the way you mentioned, pull the coil and plug, ground the plug and look for a spark.
2000 540/6 Slightly tweeked...everywhere