Lots of questions, so many answers!
1.a. The Aura is an energy forcefield around the body that is made up of your subtle bodies. Within this forcefield are seven subtle bodies, each named chronilogically based on their distance from the physical body: Etheric body, Emotional body, Mental Body, Astral Body, Etheric Template, Celestial Body, and the Kemetic Template. Now, among these, what is visible to those who can veiw aura's, I believe, are the first through third bodies (etheric through mental). These are closest to the physical body and are most affected by it. As you now know, the aura is not a chakra, which is what I will be getting to next.
1.b. The Third Eye is a chakra point on the body. There are seven chakra points on the body, depending on what culture you want to follow. They go from the pelvic area up, normally but can be listed from the other direction as well: Root, Sacral, Solar Plexus, Heart, Throat, Third Eye, and the Crown chakra. The third eye, specifically, is located on the brow and between the eyes.
2. There are plenty of herbs for protection! Safety and security has been a concern of people from all ages of time, and therefore, a lot of herbs are associated with it. Start by finding some herbs that make you feel safe, at home, welcome, grounded, or perhaps make you happy. These are herbs that are good for protection magicks.
3. There is no spell for this, it sounds like you aren't getting enough nutrients or your diet is poor. I suggest eating healthy! Fruits and veggies, as well as good sources of proteins and healthy fats. Also, I recommend taking tiny doses of lithium in the morning. Very minute doses! Lithium improves the connection and signal speed and strength between the synapses in your brain, you should feel more brainy within a couple hours of taking the lithium. You could also try ginkgo biloba dietary supplements. Ginkgo biloba has been known for decades to improve brain function across the board. And one other thing, EXERCISE! Exercising improves blood flow throughout the whole body including the brain. When you exercise you are essentially working out your blood vessels, and the more they are worked out, the better blood flow you will have to the brain, meaning your brain will have more oxygen. And more oxygen to the brain improves brain function.
4. I think there are therapists out there that can help you do some memory regression, you should investigate them.
Hope I answered your questions, mail me if you have concerns. Thank you!