The main problem with the bitcoin is that its price is too volatile at the moment. It might be better in a few years.
When the bitcoin price gets higher to around $100.000, it will not be so volatile. It will be similar to gold.
That is right. When the bitcoin market cap is larger, it is more difficult to manipulate the price of bitcoin.
It depends on the size of the whale and its influence. A big whale like the Pacific Capital can manipulate it easily.