Beautifully and thoughtfully done! I really appreciate the focus on “period appropriateness” and practicality. And, of course, beauty!

Can you tell me who makes the tile you used..perfect with this design!

I'd center it on the door opening and the window. It will be the focal point from each room opening. TRY with a piece of painters tape and a balloon.

No, doesn't matter what is in an adjacent space, similar style, but whatever you like.

Measure the width and length of the room and add together for the correct diameter of the fixture. example: 12' x 12' room = 24 inch diameter light fixture for the space.

Do you need a medallion on the ceiling? I too would go for a semi flush mount. I personally do not like exposed bulbs. Think about the other lighting in the room... how about some picture lights? balance the lighting with ambient, task lighting, etc. Floor lamps, table lamps, ceiling.

You could use a crystal chandelier in LR, also. No issues with that.

I also think that something along these lines might be interesting.

https://hammerworks.com/shop/english-tudor-lighting/english-tudor-copper-chandelier/