I'm not surprised you can't go above 12 nic because you are technically sub-ohming. When's the last time you tried a coil above 1.0 in a small, MTL tank? I would suggest trying one and increasing your nic as high as you can tolerate, and no reason not to put some nic salts in that tank, either. You have some tools on hand, so why not do some experimenting? You may be able to tolerate a different nic level in a MTL tank than you did previously... It's not outside the realm of possibility. If you like your current tank, great, use it, but maybe have a secondary MTL tank for severe cravings? It's not hard to unscrew and then rescrew a tank and adjust your wattage?
And, I do agree with everyone that making progress is a big deal. I dual vaped for about a week to start, and each time I smoked, vaping got easier.

It sounds to me you might have to get a bit creative OR keep plugging along and not beating yourself up. When I fell off the wagon (badly sometimes, ooh early on I went to a concert, that was not good at all) I just picked myself up and continued vaping. After a while I got the message that smoking was counter to my desire to feel good, and that helped me vape through many experiences. That's when I knew I'd succeed....
I'm not a big fan of tobacco flavored e-juice, but it seems the NET get the best reviews, so you could try ordering a bottle of that, if it's the taste you are missing....
Anna