[quote user="Andrey Dodonov"]1) Should I call erasing every 512 bytes? (every segment)[/quote]
I am not sure I understand this question. You shall erase segments one by one. By doing erase whole segment becomes erased.
[quote user="Andrey Dodonov"]2)Which type of writing would be better? (I know that long-word is quicker, but still)[/quote]
One that's better for your application. Unfortunately you don't specify data you want to write - it's one bit or hole segment or in between