OK.
Now you've got 1 of 2 ways to proceed... tell me which you want to do so I know what you're doing.
1. This will probably take the longest. Basically we'll resize your main partition from 44gigs, to.. probably 150-160ish, then put a swap partition on the end. This will take longer, and the system will probably have to run a filesystem check when you reboot. The good thing is, you won't have to do anything after this as long as plex doesn't fill up your root partition (which at approx. 150gigs.. it really shouldn't).
2. This will probably be quicker, but you'll have to follow those instructions I gave you earlier on moving your container folder, creating symlinks, etc. Basically you would split the 173gig partition you have now, into two.. a swap partition, and large 150-160ish partition that will be formatted. You can then move your containers to that partition and create symlinks as i told you above. The advantage of this, your containers will be off your main your partition, so you wouldn't have to worry about the server not booting from a full root partition, should your plex database become humongous.