Snake suck in feed mode, or has he turned evil?

[C&H Exotic Morphs]

A 90g rat seems fairly small for a 1200g ball python. 10% of his body weight is 120g, and that is the low end of the feeding "rule of thumb". Possible he is still hungry?

I'm feeding my 800g ball python rats that are bigger than that.

The 10-15% rule of thumb is for hatchlings and juveniles, not adult BP's.
We feed our males 1 small 60-80 gram rat every week and our females top out at about 120-130 gram rat every week. The females may occasionally get something that is slightly bigger, but never anything over 150 grams.

More frequent and small feedings make them jumpier in my experience, the small meals are just not filling enough for them to realize they don't have to hunt and eat everything that moves in fear of going hungry.

I have to completely disagree with you on this statement.
All of our animals get fed smaller meals on a weekly basis and it doesn't make any of them "jumpy" or always hungry. Besides a couple of animals in our collection that are always little jerks and don't like to be bothered at all, the rest of our collection is perfectly fine 99% of the time and aren't 'jumpy" or "sketchy" at all.
Now when it comes to feeding day all bets are off!