It seems there's tons of misinformation on how blood moons actually work, which is unfortunate. The current accepted answer is totally wrong for questions 1 and 2. Blood Moons have absolutely nothing to do with enemy kills. They are simply based on a timer.
A few days ago I posted a pretty in-depth explanation of how time, blood moon and Lord of the Mountain spawns work here. Here are the relevant parts about the Blood Moon scheduling mechanism:
[...] It turns out that time, Blood Moons and the LotM are all handled
by the same system (which I'll call the time manager) and based on
time, so first let me clarify how time works.
How time works in BotW
Internally, time of day is stored as a float in the [0.0, 360.0]
Every game tick
[...] if there is no active event/cutscene:
- The game timer is incremented by 0.0083333 * elapsed frames. Effectively, this means that 1 in-game minute = 1 real-life second.
- If the timer reaches 360.0 (midnight), the game performs special checks. See the next section.
- A value called the blood moon timer is also incremented by 0.0083333 * elapsed frames.
Every time the timer reaches 360.0 (midnight)
If a Blood Moon is scheduled:
If Blood Moons are "prohibited" (see below for a full list of
conditions), the timer is set to 2880.0 and nothing happens.
Otherwise, the Blood Moon cutscene
is triggered and the timer is reset to 0.0.
The game then determines whether to schedule a Blood Moon or not:
If the 'FirstTouchdown' flag is set (i.e. if the player has left the
Great Plateau), and if the Blood Moon timer is > 2520.0 (7 in-game
- The WM_BloodyDay flag is set to true, which means that a Blood Moon is scheduled for the next night.
- The Blood Moon timer is reset to 0.0.
Otherwise, the "Bloody end reserve timer" is set to 150. This ensures
that WM_BloodyDay is cleared 5 in-game minutes (= 5 seconds in real
life) after a Blood Moon occurs.
Blood Moon inhibitors
If any of the following conditions are true, the Blood Moon cutscene
will not be triggered.
- Not on MainField (main overworld)
- IsInHyruleCastleArea is set
- LastBossGanonBeastGenerateFlag is set (fighting Dark Beast Ganon)
- BloodyMoonProhibition is set
- Wind_Relic_BattleStart is set (Vah Medoh battle)
- Electric_Relic_Battle is set (Vah Naboris battle)
- Water_Relic_BattleTime is set (Vah Ruta battle)
- Something involving the Sky Manager
However, these do not prevent the Blood Moon timer from advancing, or
the WM_BloodyDay flag from being set. [...]
Time starts at 05:15, not 11:00, and flows normally until 11:00 is
reached. Activating the Great Plateau Tower sets the time to 11:00,
shows the time on the UI and restores the normal flow of time.
Blood Moons occur at midnight if and only if the WM_BloodyDay flag
is set. As far as I can tell, there is no way to force blood moons
to be scheduled.
That flag is set the night before at midnight if you have left the
Plateau and if the Blood Moon timer has reached 7 in-game days. Not 7
days and 15 minutes, but exactly 7 days (2520/360 = 7). Also, note
that you do not need to pass time at a campfire after the
WM_BloodyDay flag is set.
The Blood Moon timer starts ticking as soon as you've left the Shrine
of Resurrection normally. Any time spent in a state where even the
main game timer is paused does not count. However, you do not
necessarily need to be in the open world: time spent in shrines,
divine beasts, etc. does count.
Passing time at a campfire or sleeping repeatedly does not help
trigger a Blood Moon at all. Quite the opposite, as the timer does not
advance during cutscenes.
Let me be clear: killing enemies has absolutely no effect on blood moons. The time manager code does not even check for enemy kills... which proves that it is just misinformation.