The reading and writing part surprises me. Is that different from English? I don't remember what it was like to learn it in the first place so I don't remember if I initially had trouble writing something I had read.
Yes, most other writing systems, including English, use phonetic alphabets. If you learn the set of letters, you can at least sound out any word, and make a good guess at spelling something you know how to say. Chinese is a logographic writing system. There are thousands of "letters" that you have to learn individually, and there are generally only hints in the logograms about pronunciation or meaning, so you're basically memorizing how to read and write every single word individually. If you don't know how to write the character, you can't "sound it out" like you can in English. You're just stuck. This also leads to frustrations in even using dictionaries to look up word meanings.
However, even after all that time I was only able to read and write at an elementary school level. Reading, writing, and speaking any dialect of Chinese are basically three separate skills. You can easily know how to say words and have no idea how to write them, or know the meaning of a character, but not know its pronunciation, or my favorite - be able to easily read an entire sentence, but then only know how to write half the characters properly if asked to write it out 5 minutes later.
So, in my opinion, yes 5500 hours would get you to spoken fluency in Mandarin without too much difficulty. But unless you are really good at memorizing things (I'm not), don't expect to be able to read and write at a native level in that time frame unless you had exposure to written Chinese growing up.