(1) yes, the "1usd worth of STEEM" is just a means to give confidence to the people, but i believe the ultimate goal of the SBD is to have a parity with $USD, as descript in White Paper(pg15)
hence, when "1usd worth of STEEM" is not enough the derived the desire 1:1 peg, witnesses should try to gradually increase the amount of collateral, until a new balances is found.
(3) as mention in the post, this is the Impossible-Trinity problem.
If our priority is to have a fixed exchange rate, then we shouldn't stand still with the fixed monetary policy (interest rate)... if we want more control on the interest rate, then we will never had a stable SBD.
Totally agree with your point that the interest rate should be discussed and vote. but this should be done periodically, and adjusted from time to time according to the market environment... When is the last time they have a meeting or discussion?
I think the collateral and a 10% APR should be enough to hold the peg, the reason you see a price below 1 dollar now is because of a downtrend that keeps the exchanges price below the 7 day average shown on steemd, if or when price of steem stabilizes or increaes then you will see SBD at 1 dollar or above... I personally dont think we should assume that the SBD will be 1 exact dollar always, it will most likely vary from 0.80 to 1.20...
SBD has been alive for exactly 1 month today.. it has been below 1 dollar and it has been well above it too, so in my opinion is too soon to be thinking of changing the interest rate.
Exactly right that it will fluctuate. With the current "slow" incentives it appears SBD will be overvalued in a bull market, and undervalued in a bear one. It's just reactionary and slow to change the peg, which is why it would be interesting to have faster incentives to keep the peg as well!
Furthermore, i believe that the voting system here is to allow individual witness to publish their own figure of interest rate, (the 10% is just a default value which could be change anytime) just like the way they publish Steem/SBD price feed... this is the central spirit of cryptocurrency, i.e. decentralization, anti-collusion.
then the system will choose the median value from the sample. Correct me if i'm wrong.