This is a really awkward space! What about trying to build a unit into the corner which seems to be dead space. This could house the television and other bits like dvr,amp etc. The unit could then extend out towards the door in length and in height either up to the start of the window or up to the start of the blinds. I would suggest drawers for toy storage and books above. In this way you leave the windows clear for light plus it looks like you have a pull down screen so the tv would be out of the way of that. This arrangement would also hide all those wires and cables! Ikea have some good examples of storage which you could adapt or copy, such as Besta which illustrates the extended toy storage. http://www.ikea.com/gb/en/catalog/products/S39927155/

You need something heavier than the little edge mounted ones and so for all areas where you plan on using pulls, I would select the same pull, making it a good sized one.

For a room so small, you really need to get smaller items if you want to include your key board and guitars. Take out the large bookcase and get a smaller one. Are all those books necessary? Get a couple of smaller filing boxes that you can slide under the work table. Scan your important doc's and start shredding. Hang the guitars on the walls and put keyboard against the wall after you get rid of that huge bookcase. The room need major de-cluttering. I worked for years out of a home office and it can get the better of you.

Get rid of that bulky corner pantry because it dominates the entire kitchen visually and floor space wise. A well designed cupboard pantry flat against the wall will hold all you need and free up floor space for a larger counter/bench or possibly an island if you wish.