OOMScoreAdjust=Sets the adjustment level for the Out-Of-Memory killer for executed processes. Takes an integer between -1000 (to disable OOM killing for this process) and 1000 (to make killing of this process under memory pressure very likely). See proc.txt for details.
Starting with version 183 systemd provides full support for hardware watchdogs (as exposed in /dev/watchdog to userspace), as well as supervisor (software) watchdog support for invidual system services. The basic idea is the following: if enabled, systemd will regularly ping the watchdog hardware. If systemd or the kernel hang this ping will not happen anymore and the hardware will automatically reset the system. This way systemd and the kernel are protected from boundless hangs -- by the hardware. To make the chain complete, systemd then exposes a software watchdog interface for individual services so that they can also be restarted (or some other action taken) if they begin to hang. This software watchdog logic can be configured individually for each service in the ping frequency and the action to take. Putting both parts together (i.e. hardware watchdogs supervising systemd and the kernel, as well as systemd supervising all other services) we have a reliable way to watchdog every single component of the system.
Also, you're going to continue to see problems with systemd if you expect it to be just an init. It just isn't