Is there such a word as staticness?

There are at least two aspects to this question: will people understand what you mean? will native speakers regard you as a competent user of the language? You might be concerned with the first and only the first, or you might be concerned with both.

You have formed a word by analogy with other abstract nouns, tacking -ness on the end of an adjective. That shows an understanding of how English works, and any speaker who knew what the word static meant should understand what staticness meant, at a very basic level.

But since there is already a word, stasis, native speakers (or other fluent speakers) might wonder why you didn't say stasis. Are you trying to distinguish your concept from stasis? Some of your readers/listeners might get side-tracked.

When writing and speaking with the goal of being understood, it's always best to consider the possible effects of departing from the tried-and-true. Understanding is in some respects like water: it leaks out through any opening you give it.