Unfortunately, someone got a bit overzealous and thought it would be a good idea to use a chemical rust remover.
Just for the record, that wasn't really over-zealous. It's perfectly OK to use a chemical rust remover as and when needed to treat rust on any woodworking tool, as long as you follow this with appropriate post-cleaning treatment. That's all that was missing in this case.
it also seems to have damaged the surface. Perhaps there was a coating it removed. Now it is discolored, streaky, spotty, and seems to rust easier.
Yes I think it's likely it partly removed the factory-applied protective coating (which could have been as simple as a spray of mineral oil) leaving parts of the surface exposed to moisture in the air.
How can I safely clean and restore the surface?
I'm not sure I want to promote them given how much the retail price has climbed in recent years* but I've read many extremely favourable reports on the Sandflex blocks for this kind of thing. Where steel wool or Scotch-Brite isn't quite up to the task the medium and/or fine versions of Sandflex will do everything you could ask for apparently.
*Not sure how the shipping will work out but the prices here on Klingspor's own Woodworking Shop are very good currently.
How can I maintain it?
The two main ways to prevent rusting on exposed steel and iron are oil and wax. Virtually all commercial rust preventatives are based on one or both of these, including the much-vaunted Boeshield T-9.
I'm much more of a fan of wax myself as you can apply it and leave more of it in place as a protective coating while the tool remains functional. Imagine using your table saw if the bed was oily.... ugh. But with a buffed waxed surface it's great, actually better than if untreated.
I would strongly recommend you don't buy Renaissance Wax for this, it's ridiculously overpriced for what it is and doesn't work any better than much cheaper alternatives, including the Johnson's paste wax recommended first by popdan.
You can also easily make your own paste wax if that's the sort of thing that appeals to you, see previous Answer.