First time making lemoncello and I have some questions

I used the zest from a dozen lemons and 750ml of Everclear. It's been sitting for almost 3 weeks. Some questions. I was thinking 5 cups of water and 4 cups of sugar for the syrup. After filtering the everclear and adding rhe syrup, does it need to sit a while longer? And can I add lemon juice when making the syrup to make it more "lemony"?