You might want to google for anything special happening in Coloarado around your dates. It's useful to know in advance if hotel availability will be a problem.

With this sort of timing, it could be worthwhile to check a few times a week when you have time. You might want to consider whether you could change the dates or whether you're willing to accept flights at inconvenient times or with connections to use your cert (and save money).

Some people here might have insight about when (particular times of day and even days of the week) DL is likely to open up fare class availability for March, which is spring vacation time for many people, although I don't associate spring break with Denver.