I wouldn't feel it fit with no wall to the left.

I have lived in that floor plan ... well, flip-flop the staircase and make the kitchen a "U", and I lived in that floor plan.

Yes, definitely keep the closet. The house would be "too open" without it.

Is this a modular home?

Yes.

Suggest drawing that dining table & chairs (or bench) to scale as I think that will significantly affect balance in the room.

I like the plan as drawn....I would not open up those walls at all

I agree with CLC. Keep the plan as is. Make the living room your office.

You are not allowing enough room for a dining room table. If you want the table there, then use the whole room.

In the family room, skip the fireplace and use book shelves surrounding a tv.

This will give you more space in the family room. See if you can totally remove the small wall between the kitchen and family room in the original plan.

Can you move the door or window in the kitchen closer to the family room?

Move the sink and window farther from the stove. Add a bank of drawers or trash pullout to the right of sink.

I think you are trying to fit too much into the bathroom. Put a nice shower/tub in the hall bath and a nice shower in the master.

get graph paper and draw your plan to scale. Cut out tables,chairs, sofas, beds, dressers, tubs vanities, and showers. Use real dimensions for the cutouts. Lay it out to see how it fits.

In the master I would expand the bath and closet to where the double lines are drawn. Ie the middle axis of the house. You should then be able to fit a tub in there too. I would also consider putting the bath on the outside corner and add windows and then put the closet where the bath is currently.

Put the fridge to the left of the dishwasher or else you’ll never use all the counter space on that island.

Keep the closet. It helps break up the space.

I think leaving the office where you've designated it is best. It will provide space as a bedroom if ever needed - whereas modifying the actual living room as a bedroom would not work. (I've broken my ankle... so glad I could recoup on the same floor as the kitchen and a full bath.)

The dining table won't fit as drawn. The tiny wall between kitchen and family/dining could be removed. Bench seating is always annoying to anyone forced to sit in the middle. Always. You could move the couches down further into the living room area. If you keep the fireplace, move that down as well. Centering the thing is less critical than actually feeling comfortable in your space.

How many are there of you, and what ages are the children?

Don't know if it is possible on a modular home, but do see if you can add more bedroom windows on those walls that have no windows at all. Natural light is wonderful!