Shia Islamic Argument for the existence of God

[Neo-Scholastic]

Step 4 to step 5 is non sequitur.  From step 5, the argument is invalid.

The validity of that step comes from Way 1.

There is no reason to believe that space-time, dark energy, gravity (and who knows what else) are not eternal.

Whether the universe was created or eternal has no bearing on the demonstration. It works either way. Gravity et al may be both eternal and contingent.