Hi
For “normal h1, h2, h3 header, it shows up in the loveloblack font”, it’s a known small bug, the quick solution is use the following CSS to reset the font family
h1,h2,h3,h4,h5,h6{font-family:"New Font Name";}
I will fix it in the next version.
For specify the font weight, I think you need to find the CSS selector first with chrome developer tool or firebug, then, add custom CSS like below
.css_selector {font-weight:normal;}
For chrome developer useage, please refer to the following article or video
http://dailypost.wordpress.com/2013/07/25/css-selectors/
https://www.youtube.com/watch?v=V2aAEzlvyDc
Thanks