More important or more importantly

English as a Second Language English Vocabulary, Grammar and Idioms
1

Which is the right usage in the context mentioned below?
Statement 1. Statement 2. More importantly, statement 3. or
Statement 1. Statement 2. More important, statement 3.

2

This question really needs more context.

3

I think “more important” uses in case you are making comparison. And, “more importantly” is about to make emphasizing/stressing/pressing.
Ex: It is more important than …
I love my girl friend because of her kindness and, more importantly, sincerity.

4

While some tools exist for assessing software usability, they typically are proprietary. More importantly, they do not do a good job of assessing usability across domains.
I would like to know, whether we can replace “more importantly” with “more important” in the said sentence?
If so, does it make any change to the meaning of the sentence?