1.So far,bitcoin halving events have all been positive events for this currency.This is quite expected as the supply is gonna half the demands for bitcoins are gonna keep rising through the time.one of the factors that determine the price of anything of value fundamentally is demand/supply fraction.So with that view its gonna be positive but halving may damage the mining network for a limited time.It doesnt seem a big mining crisis to me.
2.In short term,of course all the major stocks are gonna be damaged by the outbreak as the economy is effected by the outbreak in wealthy countries in europe and US And Bitcoin is not an exception.Demands for cash will be higher because of financial panic and people would like to sell.So in my opinion it has a neural/negative effect on the bitcoin.
3.It becomes harder definitely .But the amount of difficulty depends on how the outbreak is gonna turn out at the end.We might be at the beginning of a financial crisis for the whole world.New projects are no exception