CBEAR,
I don�t see why you couldn�t replace some of the salt in your rub with Tender Quick. Keep in mind that TQ contains sugar and its granularity is much finer than table salt, so it won�t be a direct 1:1 salt replacement. You will have to experiment with the quantities since too much will make your brisket corned beef looking; red all the way through.
When I have cooked briskets in my offset rig, I get the smoke ring only on the non-fatty side. Sometimes the fat is very thin on parts of the flat and I�ll get a some smoke ring development, but it�s mostly on one side. This is also true when using Tender Quick, however, I have only tried this a few times. Perhaps my concentration of TQ, or curing time, was insufficient to penetrate the fat layer.