Default [Q] ROM's and Sim unlock on ATT's T217A?

I'm an android newbie and recently purchased an ATT Galaxy Tab 3. I bought it thinking that all LTE versoins of this tablet would have the ability to make voice calls, but it seems to be very difficult to make that happen on this version. The stock dialer is disabled on this version, and even though I could make voice calls with the help of Google Voice ot MagicApp and can download other dialers, all aftermarket dialers rely on the stock one to make 911 calls. It seems silly to have a communication device that can't call for help in an emergency.

I see that people have had sucess rooting this tab with kingoapp. That is great for enabling some root only apps, but I would really like to enable the stock dialer, unlock the SIM and remove the ATT bloatware. I may have actually enabled the stock dialer already. I used QuickShortcutMaker to give myself a "Factory Mode" shortcut that opens up a dailer. I don't know if that dailer can be used by aftermarket dailers to call 911 now or not. Would I have to run that Factory Mode shortcut at every boot to enable it? I don't have an active SIM to test it with right now. (I'm thinking of ordering a SIM from Cricket btw)

I've read that ATT had the bootloader locked on this device (Is that different than on the 217S and 217T?). I understand that means that I can't flash a new ROM, but have seen xposed mentioned as a way to get rid of bloatware. Has anyone figured out how to unlock the bootloader yet? If I mess something up does having the bootloader locked mean that I can't flash a recovery backup? That sounds risky and is the reason for all these questions.

Thanks!