My main advice is that you need to realize that while you're really smart, it isn't so much that you're that intelligent, but rather that you think very differently than most other people. Almost every difficulty that an INTJ faces that is unique to being INTJ arises from this singular observation.
Realize that you are intuitive, not logical. The "T" part of your INTJ typing is secondary. You use logic to determine that your intuitions are correct, especially logic involving empirical data and facts, not abstract principles.
You probably already know this, but you live inside your head. Remember that most people don't. When you are with people, try to be present. Learn how to translate your thoughts into their terms: your thoughts in your terms are not only useless to others, they can't be used to connect with other people. When you finally figure out how to translate those thoughts, people will be surprised at your insights, surprised at observations that you think are obvious.
You have very specific ideas of the kinds of things that you want and you like. It is easy to unthinkingly close yourself off from new options. Let me assure you that you don't know what you want. When you learn what you want and like, you will surprise yourself. As an introvert and a nerd and someone who feels most comfortable retreating from the world, the things you truly want and like will only be discovered by you when you interact with the world. If you want to know where to look for such things, your tertiary and inferior functions, Fi and Se, generally indicate what you need to learn and how you need to learn it.
That your tertiary is Fi should point you to the fact that in spite of being INTJ, you feel things very deeply. Heh, well, you're a 4, so you already know this, but it is more than being a 4. There is a kind of precision to Fi that most people (even Fi doms) are unaware of. Every feeling is its own thing, its own identification, its own label. Think of it like driving a car, and being aware of the sounds and the smells: the purr of the engine, the squeak of the frame as you go over a bump, the smell of gasoline - or worse - the smell of burning oil. The same way a CHANGE in these sounds/smells would alert you to an issue with your car, your feelings alert you to things that you can't even put into words. There is no why or how, the way your normal Ni-Te processes work. In Fi, the feelings just are. They contain a huge amount of information.
As a type 4, you need to realize that your feelings are not your identity. Your feelings are signals. Also, Fi isn't "your feelings" either. Fi is the process you use to evaluate your feelings. As you gain experience understanding and reading your own feelings, Fi is how you discern what the feeling has to do with. Fi is how you listen to yourself.
Se is more problematic, especially as it is connected to Fi and usually opposes your dominant Ni. Ni doms tend to use sensory experiences in order to block out unpleasant or distracting sensations. This can be as mild as drinking a cup of tea while focusing on reading a book, or as severe as dosing up on illegal drugs to block intense emotional pain/trauma. As such, it's important to find healthy outlets for your inferior Se tendencies. As bookish as most INTJs are, there is a strong tendency to find physical activities that are healthy and pleasant, including running, yoga, dancing, martial arts, sailing, hiking, and so on. (Notice that most of these are solo activities, and none are really team activities.)
The main point I would agree with from the link you provided is that INTJs are "systems thinkers". INFJs also think in terms of systems, but they see the people systems more readily than the technical systems. INTPs are also systems thinkers, but their approach is rather different, relying more upon logical consistency than intuitive understanding.
As a "systems thinker", you readily see how complex systems work. Early on, your intuitive models will tend to be naive, but with experience, you'll start to intuitively see all the interactions that most people miss. You're the person who will instantly see that a plan will fail because the person who made the plan was unaware of feedback effects and unintended consequences. Being a "systems thinker" is where most all of the reputed qualities of the INTJ come from: the strategist, the mastermind, the villain, etc. To you, everything is a system, and you understand it intuitively. About the only thing that your systems analysis fails at is people.
Your learning style seems to be full of "ah-ha" moments. This is how you use your intuition to study systems. You try lots of naive ideas out, test them against reality (Te), and none of your guesses seem to work. But, after messing around with it for a while, you suddenly make a guess, it works, and the rest of the system is obvious. I point this out because it's useful to know when you know enough. It's easy for an INTJ to assume that they understand a system even when they're totally ignorant of it. You need to dig in and "mess around" with a system for a while, until you get those few "ah-ha" steps that teach you what the system is about. Never pretend you know something you haven't actually messed around with, yet.
As for your weakness relating to people, this same advice applies. Mess around. DEAL with them. Don't retreat inside your shell. Keep an eye out for the intuitive, thoughtful types, but don't reject the rest, either. Messing around in this case, however, doesn't involve your usually Ni-Te messing around, where you take complete control of something and manipulate it until it yields its secrets. People don't like that. You can't just push buttons and watch what happens. You kind of have to turn off your mind and relax around them (i.e., be less Ni-Te and more Fi-Se). Be laid back, non-controlling, and let them be welcome in your presence. Don't manipulate, just welcome and watch and be there for them. Don't require the interactions to be deep. (Though if an INFJ wanders up and starts talking philosophy with you, go for it!)
That's about it, for now. I could probably come up with more, in time. I'm a bit better at answering the "what should I do in this case" questions, since those are usually well-defined enough to allow for specific answers. General advice is rather more difficult.