Waiting for Green Card for 180+ days now, pls help with filling out some basic info.

I've been waiting for my permanent resident card for over 6 months now. My 2 sons with whom payment was made at the same time, and all 3 of us even share the same DOS Case ID reflecting that. They received their green card in 2-3 months, but despite all information being technically the same including the address, nothing has come so far.

I went to 3 infopass appointments and now that it's been so long, they told me to just file an e-request.
I'm trying to file an e-request via the USCIS website right now. I'm almost done filling everything out, but just 2 questions if you don't mind:


1. Form #: My understanding is that the green card is I-551, but that option doesn't exist.

2. Date Filed: I have a receipt that I paid for the green card application with me and my 2 sons' A-#'s on that payment receipt made on Sept 8, 2018. Is this the "date filed?'
Thank you.
My father in law renewed his green card last July it came last week. Maybe theyre just back logged??
I submitted an online report re: the lost permanent resident card, requesting a status update at least. It took 6 weeks for them to provide a response, but USCIS revised status update that they'll remake and resend it. It came within a week or so of that status update. Literally got my green card just a few days ago.

I don't think they were backlogged. I believe it just got lost in mail.