Is it appropriate to ask the editor which changes he/she thinks is critical to the review? After months of waiting, I finally received the reviews for a letter I submitted to a IEEE journal. It’s a 3 page letter, and the first reviewer just had some clarifications regarding a figure and said the paper needed minor revisions. The second reviewer also bought up the figure that the first reviewer mention, but also said he wants us to "do more experiments" without saying what experiments we should be doing, or more "direct simulation results" without stating what he means by "direct simulation results". I did provide "direct simulation results" (atleast as per my understanding of what he would mean by direct simulation results") in the paper which I am going to highlight in my comments to the editor.

When I go to the main website, the status of the paper reads as "needs minor revision", which I am guessing is the interpretation of the editor-in-charge. It would be almost impossible to do further experiments at this point, especially since we got a 2 week submission deadline 1 week back. The original letter from the editor-in-charge also mentions that I can ask for a extension, if I cant submit within 2 weeks. 

All the other points that reviewer 1/reviewer 2 bought up can be handled, and I will address them individually. However I am not sure whether the editor-in-charge even considers the 2nd reviewers concerns about "needing major revisions" seriously, since the main website mentions that the paper needs "minor revisions".

Is it appropriate to clarify with the editor regarding what he thinks about the experimental section, and whether I need to address it, by informal email? 

Or should I just address all points as is typically done in replying to a review (and provide justifications for why we are not providing additional experimental validation), and hope for the best?
I am not in your discipline (I'm in the health and social sciences). I have always learned that it's best to try (somehow) to address all of the reviewers' concerns. That being said, reviewers are not always clear (as in your case), do not make reasonable suggestions, or their suggestions conflict with other reviewers' suggestions. 

My suggestion is to revise how you describe the experiment and results. See how you can make your description of these things more clear. Then, when you write your response to reviewers' comments, you could say, "To address concerns by reviewer #2, we have revised and clarified the sections regarding our experiment and results. The time frame provided for the revision does not allow for additional experiments. However, if the editor feels that such work is necessary, we are open to further suggestions on improving the manuscript."

This way you do not look like you are disregarding the feedback from the reviewer and demonstrate your willingness to try and address his or her concerns. Good luck!