Everything you need is under the "Docs" link in the top right corner...
For anything else you'll have to ask specifically what it is you wish to know..
General questions like "How do i code a theme" cover way to many things for anyone to sit here and write a blow by blow account of the procedure.
If the guides you've seen are too basic or too in-depth, then start with the simple ones and just pick out what you need to know, at some point the more advanced topics will make sense to...
For what it's worth the CSS on that site is far from being unfriendly, i've seen far worse CSS, and it does look quite minimal.. though i'm sure to some people it can look like alot. There are a few things i spotted in your current CSS that certain browsers will not interpret.
tag > anothertag
Some browsers will not interpret either of these selectors, quite simply they're not fully supported.
The above are referred to as sibling(second) and child(first) selectors. Although most major browsers will know what to do with these, not all will. If you have no idea what i'm talking about then disregard what i've said as you'll likely not be taught to use these in a standard CSS guide/tutorial anyway (well not a sensible one).