So here's my timeline and more details.
"Ready" at embassy - Feb 16
DS-160 Completed - Feb 17
Medical - March 8
Interview - March 27
Interview Instructions - ???
On Tuesday, our congressman received an email from the immigrant visa chief of at the Warsaw embassy saying that they are processing our case and that we shouldn't have scheduled the interview without receiving instructions (the letter only says they're ready for you). If they're not ready for us by March 27, then they will reschedule us. If they are, then we can go ahead with the appointment.
Two other Warsaw K1 filers also had their received date on February 16. One, like us, has received nothing. The other, received an automated email asking her to fill out the DS-160 (apparently this is typically sent prior to them sending an email saying they're ready for you).
All of this to say I'm very frustrated and exhausted from all this uncertainty. Based on VJ and others who we have been in contact with who had a K1 at the Warsaw embassy, their cases have not taken more than 2 weeks. Two Feb 2 "ready" filers, had gotten their instructions within 2 weeks. I wish they would be more transparent and helpful.