Hi there, Nice work !
Looks good, Yes I would use the RTC and set a timer after what you think is suficiant time, either go back to Sleep or Alarm for an action to be taken. either way your’e in the ball park.
You may want to try another approach inspired by msfujino’s System_ON_Sleep of XIAO BLE This is one of the BEST threads on Xiao Sleep as it pertains to nRF52840 how ever some of it can apply to ESP32C3
My logic would be Power up , initialize, send a BLE test message and set time & date., store Epoc Time, Go to sleep. When door is opened Wake up compare epoc time send info, wait for door closed or “door left open” alarm , go to sleep… Rinse and repeat.
something along those lines.
HTH
GL 
PJ