While there's lots of questions to be asked here, let's start with what's your current pm.max_requests setting in your PHP-FPM pool setup?
Exit code 1 in PHP-FPM typically means "general error", not a graceful shutdown. The timing in your logs suggests the child process ran for ~44 minutes before dying, which points more toward hitting a configured limit rather than a crash from a specific request. Check and adjust that setting and go from there.