Inactive Recognized Developer
Oookay, you appear to have completely misunderstood everything about WindowBreak and the types of unlocks it gives you. I'm not sure how, but I'll try to help.
First, your SIM-unlock. You've put the T-Mobile SIM card in the phone, right? Sometimes you need to do that before entering the unlock code (on some phones this isn't needed or possibly even should not be done, though, so try with no SIM or an AT&T SIM). Also, of course, make sure the SIM card is seated correctly in the phone before you turn it on...
Second, WindowBreak is a developer-unlock (so you can install unsigned application bundles, called XAP files) and an interop-unlock (so you can install XAPs with a restricted permssion flag and can install an arbitrary number of XAPs). Nothing more, nothing less. Anything else that you want to do with WindowBreak, you'll need to first install an app that does it for you (for example, if you wanted to remove mobile operator branding from your phone's registry).
Third, I doubt that 8107 is going to solve your problem (it's an incremental OS update, not a full ROM re-flash), but I suppose it's possible. If for some reason AT&T still isn't rolling out that update, you can use the CAB sender tool to forcibly update your phone. I strongly recommend you use the update uption that takes a backup so you can restore the phone to exactly stock configuration if it turns out that you do need to sell it back.
Fourth, sadly, there's no public way that I currently know of to fully flash a Focus Flash, even with a stock ROM. You may have wanted to ask that dealer for one. I'm sure that such a tool exists, but I've yet to actually see it. The tool used for gen1 Samsung Windows Phones does not work with the gen2 models.