I am sorry that this question doesn't answer to the case of four consecutive third tones, especially in what Wenlin dictionary calls "Fixed Expression"?
How should I apply what is written in one of the answers to the above question:
It depends on how you separate the words, to determine which rule should be applied.
The fixed expression used in a sentence shouln't be pronunced regardless of the said sentence?
So how to pronounce "小打小闹" in 我的一点成就 不过是小打小闹?