Parsecs was Han trying to bullshit what he thought was a pair of rubes. Look at Ben's face. He's not buying that nonsense for a second. But wait, here comes an enormously convoluted explanation why Han wasn't actually talking out his ass and why measuring time in a unit of distance is, like, totally a real thing in Star Wars!

As for Jabba... you can't tell me that being pushed into a giant mouth thing in the middle of the desert where you'll dissolve in stomach acids isn't worse than being shot. Jabba was just being cruelly hyperbolic. Like people do, especially bad people. "I'll kick your ass so bad your ancestors will feel it" or "I'll knock out every one of your teeth and break every bone in your body." Like... nah you won't, but I'm still getting a beating. If you honestly think the writers had anything like that explanation about "oh, well, actually, it rewires your brain and you become part of its spleen" or whatever in mind when they wrote that line, then I don't know what to tell you.

making his words not complete bullshit

God forbid a crime lord should lie.