The total mass in dark matter should not change with time, but its density relative to the critical density will. In other words, its relative contribution to the flatness of the universe changes with time. Before the "lambda transition" where the dark energy became the dominant contribution to the flatness, dark matter's contribution had been increasing with time. Now, we think that its contribution is decreasing.
I'm not sure where your "95%" number came from. The current percentage of the critical density that's dark matter is about 23%.
Oh, and yes, the relative contributions of dark matter and dark energy do make a difference for the size and expansion rate of the universe. The relative contributions of baryonic and dark matter to the total matter budget don't impact the expansion rate or size, however.