"On a smaller note, can I please change my username WITHOUT needing to subscribe to whatever this site is providing?"

Yes; that feature was made available to all users weeks ago.

And I still find it stupid I have to pay for subscription to do so, they're taking a page off DeviantArt's book.

You DON'T have to pay for a subscription; like I said, it's been available to everyone for weeks now. Open the settings menu: click the "User Page & Profile Information" option; scroll down until you see the "Display Name" option; enter whatever you want your new Display name to be; scroll down to the bottom of the page; click the "Update Profile Information" button; and you've got a new name.