Lots of ideas....couldn't resist adding my two cents. i copied your photos and did a little cut and paste- it's messy, but hopefully gets the main idea across. i'd put your sofa in front of the large book case, chair by the fireplace, tv on the stand on the wall opposite the fireplace - so you can either look at the fire or the tv. Someone suggested using frames of one color for your photos - an inexpensive way to do that would be to spray paint them all a dark color-black goes with everything. Since your shelves are a medium tone wood, display things that are dark or light so that they contrast against the wood. Limiting your display items pallette to a few values usually helps to unify things. (I think that's why so many people want to paint the shelves or put inserts in the back to help your nice things read more clearly...some get lost). If you want to "splurge" -you may consider having a carpenter make a few solid tall cabinet doors to provide a visual break in the shelving. I'm showing 3 doors - 1 on the right side of the fireplace and 2 on the left to leave two open vertical shelves for display on each side - with things arranged to frame the fireplace as the focal point. To add some height to your big vases, consider stacking some books beneath them. Enjoy experimenting untill you get something you're happy with - good luck!

The trim in your rooms is outstanding. To "tie the rooms together", the one thing I would do is install chair rail the same color as the existing trim. The horizontal lines of chair rail will move the eye around the room and into the next room creating a flow. Chair rail is relatively inexpensive, easy to install and would be wonderful compliment to your existing beautiful trim.

Hopefully, you have investigated your existing building conditions. Have you consulted with a structural engineer as to whether the third floor framing can hold the additional live load and existing rafters can handle the changes as well as increased insulation depth? Have you talked to the building department to determine whether the available floor area based on ceiling height meets zoning requirements? Is access doable with a stairwell from the 2nd floor that meets fire and building codes? These are just a few questions that need to be asked. You should consider consulting with an architect face to face to expedite feedback that would be pertinent to your situation rather than asking us to give advice at arm's length.

My advice is to visit an independent kitchen showroom. Oftentimes they have access to more standard priced options than the big kitchen firms. Reduced height cabinets can be set at almost any height by wall hanging them, or changing the plinth height or having bespoke feet. Since standing is a challenge I presume you will also need to talk to them about pull out units (all of my crockery is in drawers which is much easier to access) you can also put fridges, ovens etc at any height making them easier to access. You might also look at different oven doors, some slide underneath or open to the side making access to the oven easier. You can get dishwashers the size of a single oven which might be easier to load and of course can be set at any height. If your overall strength is compromised you might choose bigger handles to open cabinets. If you want over counter cabinets you might choose to have reduced depth base cabinets to improve access to the cabinets above. You can get extractors that work with a remote control which helps future proof your kitchen if at a later date you find yourself sitting more or unable to stand.