At 8 months old, 150g sounds stunted for a blood python. Has he been seen by a vet? He could be in pain/discomfort from parasites or other disease, which never improves temperament.

See the reblog by @velociraptor-of-the-year on you initial ask. You bab could be wild-caught or first-gen captive hatched. (Side note: I don’t ever take any of my snakes out of their homes twice in the same day. They know that once they’ve gone home, they’re “safe from me” for the rest of the day.)

Either way, like with any relationship, it’s no different with snakes. You let him set the pace. Stay at sitting stage until he’s no longer huffing at you for just opening the enclosure. Stay at the “just your hand in the cage” until he shows he’s comfortable with that. Weeks, months, whatever it takes.

Learn his body language. Right now he’s showing you his body language of fear. Relaxed snakes don’t huff, lunge, mock-strike, wag their tails, etc. - they sit calmly, or explore; they flick their tongues. If a snake is just frozen in place appearing not to even breathe, much less flick their tongue, that’s a sign of fear. “I’ll pretend to be a rock, maybe the dangerous mammal will go away.”

Anyways, there are no precise tables of weights and measures for snake taming. That’s why it’s difficult and lots of people fail at it. You have to put in a LOT of work, patience, time, and foremost, put the animal’s needs and boundaries ahead of your own. He didn’t choose to move in with you, he’s your captive, you owe it to him.

He’s a living sentient being capable of suffering, and as his keeper, your responsibility is to minimize his suffering. Fear is suffering.

He’s an individual, not a game AI that can be made to respond in a certain way by picking the right dialog options.