High Log Space Used for model System database
I think you made a leap. If you change model to simple recovery, the log won't autogrow constantly, because that allows the log space to be re-used (and it is unlikely there is anything going on in model that would prevent that from happening). But, I don't know how you're using model. If it's being used to store objects and data that you want created in every database, maybe FULL is a better idea, and taking log backups will allow you to restore to a point in time. FULL is also a good idea if you create databases manually (using CREATE DATABASE or the UI, without attaching), and you want all of them to be in full or simple recovery by default, then that should drive your decision, not some observation about log space used.