If you're trying to make ginger beer (soda) you may be overfermenting. A couple of days really is all it takes for soda. If you start boosting the alcohol, it becomes pretty cloying.
I only do small bottle batches of ginger beer so I don't really know about your whole process. What I can offer though is my ratio for a pretty solid ginger flavor. In a 32 ounce bottle, two ounces are ginger, two are lemon, six are simple syrup, and the remaining 22 ounces are water. 1:1:3:11. I find that the lemon really seems to help the ginger flavor become more pronounced so staying close to equal proportions there is typical for me. I very a bit, but always end up back at that ratio. It's way to gingery for my wife, but most of my ginger-loving friends dig it.
The only cooking involved in my process is in the manufacture of the simple syrup.