I've answered each of those questions on past posts already, and it would be a long speech, but I do believe there are measures being taken for many of those variables.
For example, you get STEEM on your SP holdings that equalizes the inflation, so you always have the same value. If it inflates 15% you get 15% more SP free of charge.
I know, but i am only stating that we should not take steem for granted yet. As an experiment It is really sucessful, but its Future is still uncertain.
There is still a lot of things to come, and steemit Future Will depends on How steemit Inc Will act when the time comes.
Steemit so far have no direct competition, and this Will likely change this year.
Oh I don't take Steem for granted... I'll work on what I can to support the blockchain, after all piece of it belongs to me :)