This is what you can do,

1) You can resize master bathroom i.e. instead of 10' long make it 7'6" so that you get bigger dresser or you can merge the dresser in the bathroom itself.

2) Change the g. bedroom opening from the side which is marked.

3) Keep the children room opening as it is so that you get a complete wall for either sitting or the t.v. unit in your living area.

4) The yellow highlighter is the store room of size 6' x 3' opening from just opposite to the children room opening or in line with the g. room opening.

I don't think it a good idea because there is a horizontal column which is anyway in between, so no use.

If you want to dismantle the dining area wall, you can do that but only on the condition that you don't need more storage in your kitchen because wall breaking means less storage

By shifting the main door you can place the drawing room furniture in a better way

This position of the main door synchronizes with the furniture placement. If you have a better plan, no problem, but I don't think this door position will disturb you.

If you are wiling to make your main entrance door as per vastu, then check it with 81 grid vastu. As per the grid it should be in the 2nd or 3rd block from NE corner to East side.

Half vertically or horizontally?

the opening position depends totally on the furniture plan of the dining area.The size of the serving window can be 16"/18" l x 12"/14" h, the only criteria is the serving utensils should easily pass from the window.

Lastly the only way to have a comfortable working is plan it properly and professionally as per your requirements.