Howl's Moving Castle questions. [Spoilers]

[Yee199]

Ok after watching the movie I have a couple of questions about stuff that puzzled me.

1. Why did Howl have a portal to the front lines of the war?
2. Why did Calcifer eat Howl's heart?
3. Does feeding a demon parts of your body tie you to each other?
4. When Calcifer ate Howl's heart, why did he decide to build a magical house with his powers?
5. Why did Calcifer obey Howl, shouldn't it be the other way around since Calcifer has Howl's heart?

 

[lst]

I'm just gonna give my personal interpretation:
1. Because he was compelled to fight in the war for political reasons, since Suliman saw him as a powerful wizard who should fight.
2. Maybe Calcifer needed to do that to survive for some reason.
3. Yes. And as a result, Howl's magic originated from Calcifer.
4. Calcifer did that as a sort of reward for Howl.
5. Again, because Calcifer felt thankful toward Howl.