@looksfarwoman has presented an excellent answer to the first question.

At what point do you think a reasonable limit for new users to be limited?

It seems to me that the current system does this quite reasonably and balanced. If the user creates high-quality content, his bandwidth increases by itself, with the growth of the SP. Thus, user proves his usefulness and receives more opportunities in the technical plan. However, should pay attention to the fact with the recent changes in exchange rates SBD and Steem the SP growth is very slow. But, the user may at any time change the SBD on Steem to fix this "problem".