Be aware that there is a healthy level of sodium (way lower than most) and the level in a strict low-sodium diet (way way lower than most).
I can’t say if the recipe calls for more yogurt than necessary, but that is not unheard of. When I wonder about that, I surf lots of recipes and see what the range is. If you find recipes on epicurious.com, a lot of posters will comment about whether they thought the use of an ingredient was wasteful, which I also find helpful. If you lower the amount of one ingredient in a marinade, of course lower the amount of other ingredients accordingly.
Generally, marinating in yogurt for too long can give chicken a sort of an odd grainy texture, and essentially “cooks” the meat a bit, but I haven’t found it to make it rubbery. Rubbery usually means you overcooked it. If you use a brine, the window between safe and rubber is larger, because the proteins are unwound a bit by the brine. Interestingly, Cook’s Illustrated just reported (Jul/Aug 2011) that a low-sodium brine had a nearly-undiscernible added bitter taste, which was acceptable to most who could detect it. The salt substitute they used was LoSalt, which is 1/3 sodium chloride and 2/3 potassium chloride. They cautioned to be sure that you use a low salt and not a salt-free (no sodium) brand.
As for the curry, you might try a different curry powder unless you thought all the flavors too pronounced. These blends vary greatly in quality, character, and heat. Also, if the jar has been opened for more than six months, that could be the problem. Just buy what you think you’ll use in a relatively short time. Old curry powder is worse than nothing.
In the protein bars, I’d have to guess that you used too much liquid, since you were supposed to cut them up before you froze them. The freezing step may be necessary to get the bars to set up; otherwise, it may just increase the shelf life so they don’t all go bad before they can be eaten.
Try not to use new recipes when you’re tired, when you have the choice. It is too easy to make a mental error, and just isn’t as much fun. Do them the way the recipe author directs the first time, then make your changes on later tries. It is surprising that some steps that seem pointless do make a difference, but you can’t know unless you try.
As for creativity, it rarely comes when someone with no background just starts randomly changing things in a recipe. What you want is to learn the principles that make the recipes work. In my experience, that wants guided experience, whether that is via lessons (live or very well-written) or hanging with your Grandma. With that knowledge and some practice, you’ll know what kinds of tweaking are likely to yield what result, when measuring can be abandoned in favor of using your senses, and so on. That’s when the real fun starts!