One of the difficulties, specifically on the web, is the small font which seems to be an inherited problem by nature of design (font design that is).
When we were kids, I still remember the Arabic homework in schools, which was almost on a daily-basis. We were typically asked to write down a specific letter 10 times in columns, and then some words and so on. I have to say, my handwriting didn't get any better till I finished high school maybe when I got some interest in calligraphy (never practiced but I thought and still think that having a good handwriting is essential for character).
So, on the web, probably the only solution I'd give you is what other people here are doing, but zooming in whether in your browser or in the app if you are on a device. I heard also about an add-on for Chrome called Wudooh (وضوح, clarity in Arabic) which they say it enlarges the Arabic font specifically.
Outside the web, I'd advise with getting your hands on writing Arabic letters by repetition. Remember, your hand got a brain of itself.
Not sure about the argument here but anyway N ن is typically connected from both sides, but ذ is connected only from the back.
When ن is in the middle of the word or the beginning, the dot placement is typically around the top of the Sinna (the sharp edge of its beginning).
This said, in calligraphy (as an art) the dots can be manipulated.