Yes, however, I would rename it after you close down bitcoin core.  Then open bitcoin core again and try to import your keys.    This way, once you import your keys you can be sure you have everything.   Then it is safe to delete your wallet.dat.

Yes. Although it isn't readable without decoding, it only stores your private key. To spend your coin, you need your private key. Do verify if you have copied down your private key properly as you won't be able to spend your coins unless every single of your letters and numbers in the private key are correct.