I would tend to drop the matter this time but pursue it for the spring or graduation prom. The letter posted is way to long and need not be a history lesson.

Points to cover are:
Prom is very important to you and your partner.
Instead of a tux or business suit plan on wearing formal kilt attire which consists of kilt, white shirt black jacket and tie and knee socks etc.
Attire is in recognition of your Scottish American Heritage.
Have full support of your parents and partner.
Seek your agreement as this is important to me and date.
Please reply

Yours truly
name address e-mail