You can eat oat bran and buckwheat as those are prebiotic (they feed the beneficial bacteria), I would just not overdo it because they do contain some starch which could feed candida as well. This is a test food so watch for reactions.
The cereal you mention in your post scare me because it states it contains gluten. I would stay away from it. Make a home made hot cereal out of oat bran, coconut oil, stevia, cinnamon or any other spice you like.
I will let Able respond on NAC.
Any meat or bones should be organic if you can find it and also important that they are grass fed animals, otherwise they may lack nutrition we are trying to get from it. If you get non organic, grain fed meat or bones, then you risk of getting toxins, antibiotics and harmful effects from grains (which we are working so hard to avoid on the diet) with that meat/bones.
Honestly, there is no organic classification where I live, so I just get it from reputable store and hope for the best.
I have canned sardines, but make sure they don’t have any other ingredients besides fish, sea salt and olive oil, perhaps allowed spice.
Hope this helps. Best of luck to you!