EAD Timeline question

Hello guys,

I applied for premium processing for my OPT EAD Application. I went to my biometric appointment yesterday and also received a case status update on the website on June 22nd (yesterday) saying that "Premium Processing Clock Started for My Case". I wonder does anyone have an approximate on when I will receive my actual EAD card? I tried contacting USCIS but they only tell me approximately 30 days.

My work start date is next Monday 6/29, I know I need to bring this to my HR asap to request for a delay in start date but I am very anxious, I am afraid this will make them not want me and move forward with other applicant.

I also would like to know if I could start working without actually receiving the physical EAD card? Thank you!