Each of your questions can be answered several different ways. I will attempt to explain the ones I have worked with on this previously.
Overactive Third Eye:
An overactive third eye can be handled in a myriad of ways. First I would seek to learn why your third eye is overactive; do you simply believe it to be overactive because you are experiencing things? To tell the truth, most paths outside of the purely New Age ones either do not work with chakras, or do not work with them to a large degree. For those who intentionally are placed on the path of the mystic, or for those involved in the arts which "focus" the third eye, you may be quite average, or possibly below it in some cases. You have to remember that each of us is built differently, for different purposes, so your third eye activity and my third eye activity are going to be different.
It could be that the two closed chakras on either side of it are assisting in your third eye being overactive. In the chakra system, energy flows from bottom to top, cycling through each of the chakras. If you have a blockage above, you can cause a greater portion to be "trapped" at the lower chakra. Even if this is not the problem, it may help to alleviate some of your issues so I suggest working with the other chakras in ways which are helpful to you.
If you work with specific forms of visualization to open your chakras, you could also use such to close them as well. You would simply go through the reverse of it. However, I truly do think you would be better off balancing yourself as a whole as closing chakras can have negative effects on you. So if you choose to close it, make sure to only close it a little bit.
Are you trying to keep the energy with you or are you having issues of energy being sucked away from you? Is it a case of you simply feeling the natural flow of energy? Energy is all around us and within us, and it is not stagnant (though it can feel that way to us at times). It moves from within us to the environment around us, and moves from the environment around us to within us. This flow is constantly occurring, though we are not always aware of it. It is more likely that you are experiencing this phenomenon than that there is an external reason for you feeling this way.
However, if you feel as if it is being taken from you forcibly, I would work with a simple shield. Most of those external influences that would sap energy from you can be shielded against in a variety of ways, and will not return unless you let them. Create a personal shield in a color that appears protective to you. To do this, call on your energy in whatever way you do so in order to gain influence over it, take the energy and form it into a bubble, ball, etc. Spread this bubble over you widely, giving you plenty of room to move around and be comfortable in. While making this, focus on protecting yourself and your energy from negative external influences. Another step is to examine your life and remove the influences from it which are causing you undo stress. Yet another way is to work with soul retrieval, however due to your newbie status I would pursue this at a later date and work with someone knowledgeable in it when you do.
Balancing Masculine and Feminine:
Balancing the masculine and feminine can be achieve a multitude of ways, the simplest laying in you working with different spirits and/or deities that are of these persuasions. You can also work with guides who represent your inner masculine and feminine selves. However, I would focus on this after you have yourself set in working the basic things of magic.
If you need any assistance in these areas I am willing to help out in any way I can, even if that means you and I have to sit around working on shields for a few good hours. :)