It's too late to add the tenderquick in my opinion. Reason being, for it to penetrate right through the slab of meat, you'd need many more days. Consider that the bacon has already been in the cure for 6 days, all of the meat juices and insterstitial fluid from the bacon has ALREADY come out and you already have a hard slab. You're not going to get the tenderquick to get in. That's just basic chemistry..
Second, the Sodium Nitrite imparts certain colours and flavours that you come to associate with "the way bacon should look. If you have not used it, you won't get the colour or the taste you're expecting, but that is not a bad thing.
I'd recommend finishing the process as you started it and then smoke the bacon to 165 F just to make damn sure you don't kill yourself from botulism.
I've done it this way now 3 times and so far, I'm still alive and the flavour of the bacon has been well worth the effort.
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