Would my paper get rejected if the related work section takes up too many pages, and what would the optimal maximum length for this section be?
If the papers were suggested by the reviewers, there are high chances that those papers were from "reviewers" and they wanted to increase their cite count.

In my experience (non IEEE Access), I cited those papers and the paper got accepted. No need to cite additional papers (OTHER THAN THOSE OFFERED BY THE REVIEWERS). I think because the contribution you made was based on your prior study of literature and it should suffice. 

If you think that few papers SUGGESTED BY THE REVIEWERS are not under the scope of your research, simply explain politely that "We found paper XYZ to be out-of-scope of our current research and could not fit into our paper. However, paper XYZ-2 did shared some interesting ideas. We have included a detailed discussion on this in Section ABC"... and