The Jekyll-and-Hyde comparison is more apt than Donatello probably realizes. There are two sides of Dustin currently warring in him right now: The part of him that realized his intelligence and the powers it came from were being used to further someone else's career without his consent, and therefore absolutely cannot trust anyone that feels like they're trying to understand his work or delve into his personal shit; and the part of him that has craved the recognition and company of someone with a similar intellect to his own, especially someone close to his age, and desperately wants to show them his accomplishments and just fucking talk shop like a normal engineer. He recognizes this dichotomy, even. The conflict is written plain on his face, growing increasingly pained the more Donatello rambles. Dustin wants to believe him, so badly. But he can't be sure that's a safe thing to do.

"...Look," he eventually manages, but stops short. Puts his face in his hands and holds them there for a couple seconds. When Dustin glances up again, he looks very tired. "I...get it. I am willing to show you what I've got. But--" He holds up his hand, eyes sharpening like knives. "--If you fucking blab about what I'm working on or where my shop is I will fucking find you. There's only so many places to hide and I know where all of them are. You get me?"

This is mostly an empty threat, although with how seriously Dustin delivers it, Donatello might not take it the same way.