❤ - Do they have a love interest?
Despite not having an official mission to occupy his time on Earth, and spending most of said days gallivanting around either needling/getting needled by Zim or exploring for the supernatural, which means he technically isn't busy so much, Dib nevertheless doesn't consider these things very much.
So for him, it would likely end up being a thoughtful 'no'.
☮ - Do they have an idol or someone they look up to?
Though the scientist occasionally resentfully laments about being sent to Earth regardless of not being an Invader on the commands of the Tallest, having always been studying information rather than training his muscles since smeethood means Dib can't help but still (both metaphorically and literally) look up to Tallest Membrane, whose views the Irken grew up sharing.
Which is probably why he keeps doing stupid things in the name of science.
☼ - Something that/Someone who makes them happy.
He doesn't have many people willing to voluntarily speak to him, let alone in any hint of a friendly tone, so spending time with Zib is pretty good at making him content, at the very least.
Dib also really, really likes sugar cubes. That will probably make him happy too.
✖ - Who is someone they just cannot stand?
Do you even have to ask this one? Zim, Zim, Zim. The human draws Dib's ire like literally no one else has ever managed, and any kind of death is probably too good for him. Suffice to say the Irken would not hesitate to push the suspicious, stubborn moron with the conviction that he's saving the world from an impeding alien war out of a window given the chance.
... Also, Keef, though that's less 'I hate you please go away' and more that the ever-cheerful Invader honestly freaks the Irken out.
♥ - What does ‘love’ mean to them?
Having grown up as part of the Irken Empire, where silly emotions like love are looked at funny, Dib honestly doesn't consider it at all. His thoughts are usually predominately about his inventions and experiments, so love doesn't mean much to him personally.
He does acknowledge that the kind displayed by, for example, Zim's parents seems nice however.