Question: How do I humanize him for my readers?
I think he needs a reason for his flaws, a reason a human would experience, a reason beyond the fact that he comes from somewhere else. (unless somewhere else is Earth).
Think of relatable human experience and craft the flaws in your character to those.Relatable experience is: being bullied, being rejected, etc.
For example: A character who has trouble committing to others ... is flawed (and maybe unlikeable) ... but if that difficulty is because he was jilted by someone in the past, someone he truly loved, then he is more relatable.
Your character's flaws need to stem from issues your readers can relate to.
He wasn't allowed to own a cell phone and so he doesn't know any social conventions.
He was bullied and so he is sarcastic as a defense mechanism.
He's physically weak because the sport he actually wanted to participate in is not acceptable on his planet.
Your spellings are British so I don't know what cultural ideals in your list fit within your own culture. In the US, individuality and triumph would be the two ideals most readers would at least recognize as valued cultural aspirations. SO, if you want to work off that list, try that too, for whatever culture you plan to market in (or a few).
Example: Most US kids feel like complete failures by the time they're teenagers because they aren't pop stars. They all got little trophies for things like breathing from the time they were 3 (because ... self esteem!) and they don't understand when they don't become famous by the time they're 12. It doesn't help that every disney/nickelodeon show is about 12 year olds having exotic famous lives. Most US teens would at least identify with a kid who thought they needed to triumph - and never did.
Bottom line: Pull in actual events that humans on earth work with and mold them to your world. Craft relatable events as the reasons why your character has the flaws you identified.
An overarching moral choice is also incredibly useful for hook-ability; see recent answers by Mark Baker. As a testimonial to this idea, when I hammered my MC from 'running from something awful" to "figuring out how to save something he loved" readers connected with him better. The plot stayed the same, but I recast his motivations to something he was working towards, saving someone he cared about. Instead of running from his problems, he took time away from his problems to figure out how to 'save' that person. Same plot, different motivation, seems to work better for readers.