I like it as a starting point, a minor sidenote though: What you perceive and describe as bright red links, code and sidenotes is for me, as a color blind, almost indistinguishable from the body text if it wasn't for the underlines and monospaced font. Those off-black and red colors are for me just very similar dark hues on an off-white background. If you want to highlight these elements the current red does a poor job for colorblind people like me.