Bring to your interview and carry with you when traveling the documentation that you are starting your residency in Greece and you will probably be ok. They want to make sure you are a visitor and not an immigrant. Evidence that you are starting residency in another country goes a long way to roving that.
Staying almost the 90 day maximum is a red flag that one is trying to use the visa waiver program to live in the United States which is not a proper or lawful use of the visa waiver program. The officers are trained to pull people aside who use almost the maximum, leave for a short time and then come back for another long visit to make sure they are not unlawfully using the visa waiver program. You shouldn't feel singled out for doing anything wrong; it sounds like you have done everything right (followed the rules by leaving on time; being honest when you came back; applying for a visa when advised).
Yes, you will probably be pulled aside ("detained") each time you travel here for a while due to your travel history and girlfriend here.
Just ridiculous -- reminds me of The 10000 dollar cash limit. They establish clear specific limits -- how much cash you can carry, how long you can stay, etc, but then they want to harass people for going close to the limits. If they don't want people staying 86 days then they should make the limit 85 days and not bother anyone that stays 84. If they don't want people carrying 9950 dollars they should change the limit to 9949. What they really prefer is rules that are so arcane and confusing that it's impossible for anyone to follow them, so when there is clarity and people read and follow the rules it makes them unhappy because it's frustrating their plans to turn everyone into a felon.