There's a bit of a workaround to prevent the game from crashing when using the +10 trainer, though I've only tested this for Fast Kill. But please backup your save first, this is important. Just go offline, activate the trainer, take your quest. Once you're strictly beside the monster, activate your fast kill, hit it, then deactivate it quickly. Do the same for multiple targets. There's a high chance the game won't crash. I've had a couple of quests done this way successfully. But there were also a few crashes in between, so it's not a 100% sure thing. Even had a crash in between a save even when the cheats were deactivated, hence I cannot stress enough backing up your save first before anything else. I've yet to test it with the rest of the trainer though