Starkiller doesn't have a better feat then managing to match Sidious for an extended period.
Vader was >= a Starkiller who had just blown up 150 meters of frigate, fought off an Imperial boarding Force, fought through the Kaminoan garrison, fought through dozens of clones that exceeded him in some areas and with Juno dying nearby. Hardly on equal footing there.
grew* It's GREW.
Throwing around Dooku, collapsing 30x90 meter domes, manipulating 60 meter long, 30 tall, and good knows how thick CIS dreadnaughts before several power-growths described as "vast"(going from getting overwhelmed by Ventress' inferiors with the Force, to murking Asajj with the Force in just one year being a nice example), casually hurling a tank so it has the effect of a bomb on a small droid army, wiping away a small droid army, etc.
Force pushing Dooku does not beat hoisting Vader into the air and dominating him telekinetically.
Collapsing a 30x90 meter dome when enraged does not compare to directing the descent of a 1,000,000 ton mass when concentrated.
The feat you mentioned is surpassed completely by multiple of Galen's and you can only measure his prime capabilities off the feats he's demonstrated when using his power which as mentioned is the dome feat when amped beyond a normal state by rage and landing a force push on Dooku that flung him back in a normal state.
In regards to Ventress, read above.
Hurling a tank? I think you mean sliding it across the ground and then it exploding likely due to the fuel inside. I have my copy on hand though do don't worry. I'll post exactly what happened over your biased account.