Welcome to AMAWED, @smyle! My response to your questions are

1. I do not even think that steem strenghts/rates are determined by changes in btc. My understanding is that the price of steem  is determined by **'usability'** which is the way people use the platform steemit and token, steem.  I would also add that the price of steem in the market depends  on whether or not the steem token is scarce. As in basic economics, scarcity brings about increase in value.  So if steem is scarce in the market, the price will increase, but if there is too much of it  in the market then you will see a decrease in price , just like money, which follows the rule of demand and supply. 

2. Steem backed dollars (SBD) was created as another coin for steemit to bring about stability of steem in the market. Please read more from [steemit's whitepaper](https://steem.io/SteemWhitePaper.pdf) and her [recent bluepaper](https://steem.io/steem-bluepaper.pdf) . 

3. Well, between SBD and steem, I would advice a Nigerian to sell SBD. The Nigerian should ''power up'' his/her steem, in my opinion. 

4. From my experience, I think, it's easier to sell steem on [blocktrades.us](https://blocktrades.us/). However, transaction fees are less on [ bittrex](https://bittrex.com/account/login).

Thanks  for the commendation and for participating in AMAWED.  I really appreciate.

@maryfavour