Having gone over the 12 or so possible causes of your Camry’s problem and having re-read your description, I have to think that the problem is with the torque converter. In order for the Camry to suddenly stop moving in traffic, it has to be that particular device. You see, when the torque converter goes it is a sudden failure, just as you described.
The torque converter is the first step in your transmission’s actions. Taking the power from the input shaft before it splits off to power other devices, as well, the torque converter spins up and starts moving the transmission fluid throughout the case. Without it working, setting up the current, so to speak, your transmission doesn’t work.
Now, it is entirely possible that your transmission filter could be plugged up, preventing the flow of transmission fluid. There’s really no way to see if this is the case, other than draining the fluid, dropping the tranny cover, making sure there’s a bucket underneath to catch any drips, and locating the filter to check it. You can do this work to save a few dollars as it is straightforward and only involves a wrench (10 mil or so), the bucket, new gasketing to seat the pan correctly when you sock it up and the proper amount of transmission fluid.
With that said, I honestly think your primary candidate is the torque converter, in this case. If it is the torque converter, your best bet is to insert a rebuilt transmission (transaxle, really) in place of the old one because it is a major repair and a new converter, if that is the only device swapped out, could start putting higher pressure levels on other components that may be marginal, pushing them over the edge. The rebuilt transmission will cost about $3,400.