If you haven't seen this yet, go to this
website as they traveled on Bromptons and have a lot of great tips and videos.
Not quite sure why the need for the lightest parts on a Brompton that will be loaded with 20+ kilos of gear. Kind of defeats the purpose.
Not sure why you would choose +8% gearing with a loaded bike. I personally would have went with -12%, the hills are going to hurt.
S handlebar for touring and at your height? I would think the P bar would have been better or the H bar for the added height.
You are choosing a saddle based on weight, forgetting your butt will be on it for hours upon hours. There is a reason people choose Brooks.
I don't understand any of your logic but then again I don't have ride your bike and you must have thought this out.
Good luck.