[TJP1600]

Spoiler for Spoilerless answers:

1. Well volume one strongly hints at who might have killed her. However, nothing explicitly states that Hyouka is indeed dead, she's only "missing". Nothing is conclusive from the first volume.

2. I don't really think he contemplated much about his girl situation. I believe in volume 1 he mentioned that he wants a simple lifestyle. Don't believe that view has changed yet.

3. More like the other girls become interested in him, but for Hinako, he said that he would try to resist. Key word being "try", she makes it pretty tough for him.

4. No, he wields a normal katana received from Hyouka.

5. Very likely he is

Some answers are based off what I know up to volume 5