Pankaj, I just realized that initially you told us that the bathroom area was 12'-0" x 9'-0" and later you mentioned that it was 11'-8" x 8'-0". In the last floor plan, I forgot to change the bathroom with the new dimensions. Below is the floor plan with the correct dimensions for the bathroom. The bedroom is ok, I drew it 19'-2" x 12'-6". The new layout does not change the way things are placed. Everything still fit. The only difference is that the vanity is now 4'-4" long instead of 4'-8". and the toilet is closer to the shower by 1'-0". Can you give me the lengths of the walls K and L. They are the walls between the vanity and the shower area. I will send you the new layout once you give me the length of these 2 walls.

there is no perfect dimensions for an island. Try to organce space subdividing into smaller cabinets of 60x60 cms which is the max space for a structural division and works for seating area as well

I agree with divadeva. More lights. If you can add pot lights do it. If they're already there add task lighting and up the wattage on the bulbs on the pot lights (replace with LED and you can make them brighter because the wattage on LED is lower for brighter light). If you have all of that add decorative lighting. If ventilation is an issue find a way to move the air around or add air filtration. Maybe the HVAC is deficient. Maybe you can add a HEPA filter instead of the standard one that comes with the unit. Call an HVAC specialist to see if there is a way to boost air flow in the room.

The living room window itself does not appear to be designed to let much light through. Please show a photo of that window, also of what lies outside the window. In the meantime, I suggest that you replace the builder-installed window with one of your own choosing. Use toughened glass rather than this heavy grill. Minimise the frame, if possible, particularly if there will not be much air coming through. If there is the potential of air but not much view, then have a sliding or bifold window that maximises the opening. On the blank wall outside, if that's your view, put up a green wall, creeper, something to improve the outlook. For nighttime viewing, add mild uplights in a natural white shade, focused on the greenery. Or else, you may be able to put up a reflective surface on the facing wall, to bounce in more of whatever light there is. Such as a coloured glass mural if not a plain mirror. Once you have maximised your window, move on to the wall to the right of your living room photo. That is, the wall that your living room shares with the west bedroom. Use a very large mirror on that wall to expand your living room visually and to bounce more light around. To cut down on expense/effort you can make it out of several standard-size sheets rather than one giant sheet. However, if that wall is to be covered with storage, make sure the front surface of the cabinetry is fairly light-coloured and reflective. Last, if not yet satisfied, consult a lighting expert for this room. That would be useful. These are fairly expensive solutions, all in all, but they should help.