Dear Joan,
I think you should shoot more film, for many of the reasons you mention.
First, even though you have used natural light, the direction of the light on your subject, is still flattening the form. Children of this age have such subtle soft forms to begin with, you want to get as much visual information as possible in order to describe them.
You also have a great deal of photo distortion in the focal place because of the lens and proximity from which you photographed your subject...look at the size of the feet and lower legs. You'd only be able to correct this distortion with careful drawing to reflect true proportions, or posing from life (LOL). To correct this when you take photos, you will need a zoom lens that lets you back away from your subject and zoom in.
Yes, the background has to go. Unless you plan to use a nonrepresentational background (i.e., color/value), it is unwise to invent "stuff" to fill the space, and especially if that stuff is unfamiliar to you, and even more so if it is of an architectural nature which requires precision in perspective, such as hardwood floors, doorways, windows, fireplaces, bricks, and so forth. You could solve this problem either by changing the setting in which you photograph him, or simply by draping the furniture in the background with some fabric whose colors you'd like to employ in the final piece.
I think that the idea of adding color through interjecting a prop is problematic, because you'll end up with the most highly saturated object competing with your subject (and probably winning). When you next shoot film, consider placing props with your subject, stuffed animal, etc.. With something like a ball, you will have to be precise in painting it, so it is round. In either case, I think you would be well-served to consider the overall color harmony you want in the portrait, so that you aren't just arbitrarily adding a color. If you use a prop, think in terms of overlapping forms, rather than just placing an object next to him; so put the toy in his lap or hands, etc.. Barbara Hudson faced many of these same issues here:
http://forum.portraitartist.com/show...&threadid=2063
Good luck!