The part you are showing is called the Deep Pleats and they are needed for the aprons to hang correctly and to allow the aprons to fall between you legs when you sit.
To alter a Kilt 7 or 8 inches larger is a very major undertaking and in most cases impossible with a Traditional Kilt. To shorten it is also a major re-build by a reputable kiltmaker.
New straps & buckles of the kind used on Kilts today can be found at
highlandxpress.com
Look in the sewing section.
However they are not the same as those you have on this kilt. Those style buckles are very hard to find.
If you do find a source for them please post here. Most of the kiltmakers would love to have that source.
My suggestion is to attempt to sell it by listing on this forum or perhaps ebay.
Steve Ashton
www.freedomkilts.com
Skype (webcam enabled) thewizardofbc
I wear the kilt because: Swish + Swagger = Swoon.