If yes, then how much does it increase per week
Basically yes, if you are active and keep posting everyweek. Your activity will increase 14 activity in every 2 weeks.
for some reason, my activity went from 14 to 28.. about 4-5 days after opening my account.
the 360 second rule is annoying, but it's necessary. it only took me 4-5 days of posting to get out of it, and i now have nothing to complain about.
So it only has taken you less than 3 weeks* to post 440+ posts. Such a ratio looks a bit suspect to me. Can one really be writing 20+ useful posts a day?
*) 4-5 days + 2 weeks max