Use of ン in place of の > **** ... > I was doing headstands in the house and wrecked the door and... Presumably is a contraction of . Why is it written in katakana? I guess it's adding some kind of emphasis; maybe " **in** the house" or "in the **house** "? Also, how would this sound in speech?

This is a common contraction in Western Japanese dialects. It's not emphasis. You could speak this in two ways:

>
>
>

This isn't typically written either (dialects are somewhat neglected in literature), so I would say the choice of over was on a whim.

One common (the only?) place I've heard this used in Standard Japanese is before []{}, in sentences like:

> []{}[]{}

or after someone's name:

> []{}

Note that in general, the easiest place to do this contraction is before other row words, like above.