Anxiety kicks in with deadline close... Can someone help?

Hi, i'm a newbie designer with 2 years of experience... This year I accepted a job with large prints (I usually work more in digital, but I accepted the challenge) So... I was setting up the exports for the client to print on an scale 1:10.... Even with advice that the photo was gonna crush in quality the client stuck with a photo on low res to whom I demanded to be in good quality -.- The thing is, I'm pretty dissapointed and critically let down by the job... But still want to deliver a good piece even if I don't like it. Is there anybody who works at large print workshop who could tell me if the settings are ok?

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Set the color managment to COATED FOGRA 27 (ISO 12646:2:2004) CMYK

If the actual size was 300cm x 400cm set the document on 30cm x 40cm at 720ppp (giving up with photo quality)

Render it on PDF and JPEG [8504px x 12756px] sizing between 34-40 MB seems OK...

Hope someone could help, and thanks in advance