Usually yes

This way.

You can avoid the confusion by using "חלב הוא חם" for "milk is hot".

It could, but usually doesn't. If you want to specify, you can say "חלב הוא חם"

Milk is hot - חלב הוא חם But it is a strange sentence, I think, because it means that some milk, or milk in general is hot.

The milk is hot - החלב חם When we have the definite prefix ה, we don't need הוא.

The hot milk - החלב החם Both words get the ה prefix.

The letter כ has two prononciations. It's either pronounced exactly like ק, or exactly like ח. Without niqqud (those little dots people never use) you can't really tell which pronounciation it is, sorta like the english letter C, you just have to know.

Basically, to answer your question, they're pronounced the same.

In English, yes, but a lot of languages make little or no distinction between the two.