How much time should a person spend talking about their past / track record?

• It may depend on how you do it.

Keep your comments short

• Presidents should really be training for presidential debates the way MMA fighters train for a fight. Bas Rutten trained twice a day.
• Getting interrupted by the moderator doesn't look good.
• Getting interrupted by other candidates also doesn't look good.

Have someone in the audience to give you live feedback

• It might be useful to have something analogous to a cornerman in boxing / MMA

Don't tell complicated stories

Don't reference things that people won't get

Prepare for questions that ask you about things that you aren't familiar with