[WWTBC] Book where MMC is 'married' but dates FMC

I'm looking for a book where MMC is a cop and he remains married (but separated) because she has mental health issues after she crashes her car, ending her Bsf's life. MMC starts dating a barista, and there's loads of drama with his ex.

I believe this is the first book in the series.

! MMC even calls FMC by his wife's name once by accident, and they fight over it. His ex even ends up hurting the FMC physically, but the MMC has had enough and asks for a divorce!<