Here's my guide for gold stars, which is 800k and 100%. This is the version with commentary, explaining what I'm doing and generally why I'm doing it. I've also uploaded versions without commentary, which should be linked on the video page.
On hard, enemies shoot more often and deal double damage. On Evolution, this can be a serious problem; this was one of two levels where gold stars were tempered with a need to stay alive. Save as much health for the phoenix boss battle, as that's where it's most needed.
The most important thing to remember is to keep your perfect multiplier going! The multiplier only counts for octa-locks, meaning you'll get minimal points for spamming. For gold stars, you'll want a combination of octalocks and spamming, but if you're not going for gold stars, it's best to always try octalocks, even if the enemy is about to get away. Your purification percentage takes the hit, but you get a few more points out of it.
The video's a pretty ugly run of it, but if nothing else, it shows you don't need a picture perfect run.
Also, if you're having trouble with octalocks, turn down the sound effects in the main menu. I dropped it to about 20% and the beat was very clear for me.