Based on longest wall

I would go with the way it currently is if it was my house.

Parallel to the longest wall, which is how the current flooring sits.

why not match the angle of the hallway entrance which is similar wood? otherwise you have an odd transition. I like angled flooring myself. Find it very interesting.

Problem with continuing from the hallway is that room will end up horizontal which I don't want.

Based on the longest wall. You don't want to shorten the length of the wood by installing it crosswise across the room. My wood floors start at the front door and continue lengthwise through the house. A layout of your rooms would help.

It doesn't matter. The way you show is good.