Addiction is not defined on how many per day, but on how many days you can go without one. If you feel as if you cannot go on without it, then it is an addiction.
I'm not sure I understand your question. but there are 3 days in between the seventh and fourth day you mentioned
10 Actually it would only be 7 with 3 days repeated.
That is just a general statement. There is no specific amount of days within "several days." This could be from 3 or 4 days to a year.
I assume you mean months which about 2 months are in 60 days. If not 60 days are in 60 days.
I can only see one 'days' in 'two days'. Not really much Maths there.