In my experience, I can't even see the interface until after the on-disk DB is fully loaded.  However, I have an SSD, so the behavior you describe might be normal on a standard HDD.  Additionally, I am assuming you mean until the DB is fully loaded, and taking forever to sync isn't the best term for that if I am correct.  Sync(hronization) is when the blocks on the public network (Internet) are downloaded.  This is why I specifically mentioned the on-disk DB being loaded.  Until that is loaded, it would not make sense for the interface to display any data.  However, once that is loaded it should display balances and recent transactions with a warning that you are not fully synced and they may be inaccurate.

I'm not sure how much risk there really is, but it is recommended to shut down the client before manually copying the walled.dat file in either direction.  It used to be possible to issue a resync command whenever replacing the wallet.dat file to make sure it was up to date, but I believe some things changed in the most recent versions and that may no longer be possible and/or necessary.  Regardless, assuming you only have one wallet.dat file and simply want backups, you can take them while core is running by using the command "bitcoin-cli.exe backupwallet " from the daemon subdirectory of your Bitcoin Core installation folder.

Finally, while this response may have come pretty quickly, There is a Technical Support section where you should have posted this and might typically get quicker (or at least more informed) responses to these types of questions.