re: plastic leaching.
I have moved away from having plastic in direct contact with a ferment (plastic bag filled with brine style) because my research suggests the pH of a fermented food + the soft pliable plastic of something like a ziplock bag can be problematic. But, I use those ball plastic lids linked to above ALL. THE. TIME. for storage. I really prefer to avoid metal lids once jars are in the fridge. It is a small irritation I am happy to avoid with the purchase of a 50-cent plastic lid or 24. Those plastic lids have been very durable. I am not concerned about leaching with them because they are never in contact with the food itself. reCAPs are also fabulous, but I save them for situations where the pour and/or flip lid actually makes a difference, not just for everyday storage of ferments and jams.
In terms of the rust on the rings, I don't think you can do much more than postpone the inevitable. They will eventually rust, especially when in contact with acidic ferment juices. The good news is, once you start actually canning, magically you will have 10 zillion rings and will have a new problem - where to store them when you aren't using them! ;) Oh, and just to confirm: you say you have a pressure cooker - you aren't planning on pressure canning with that are you?