I filled one out for the Philippines recently. For part 3, I did not include myself as a dependent. For part 2, I listed "self" for the beneficiary.
You are correct to put the anticipated arrival date and select "no end date"
You are also correct that Part 4 will be filled with N/A.
Remember that this confusing form is "designed" to fit multiple visa types. It doesn't work very well for K-1.
We had our interview last week. The I-134, nor any supporting documents, were collected at the interview. I'm not saying don't fill it out but be aware that the Philippines probably won't even ask for it. That also means mine wasn't reviewed and proven to be filled out correctly. I'm just telling you what I put on it. I followed a good video when I filled it out. Unfortunately, I don't have a link for that video anymore.