I'm not sure whether it can be used elsewhere such as another retailer with similar acceptance, but as far as an upgrade to V/MC, that's not available for this particular card. Maybe others who have this particular card can chime in to provide guidance on where else it can be used.
If you decide to close it, it can remain on your CRs for up to 10 years so AAoA won't be affected (until it drops off).
I am unsure if this will be helpful, but I have a former Matrress Firm credit card that turn into a Synchrony Home credit card. I can now use it at a lot of locations that use Sychrony financing, although it's very spotty. You might check on the back of your card and see if it says something about Synchrony Network. Mine has a silver stripe on it, like a Discover card, as well as a chip.