The difficulty in deciphering laws is indeed a huge problem and I doubt that many congressmen even understand the laws they pass, at least as a whole bill. Short laws aren't the only solution to this particular problem however. One solution that I've been pondering for a while is what if lawyers used Object Oriented Design principles in writing laws. They could add layers of abstraction until anyone can understand the top layer of a law, just as with OOP (Object Oriented Programming). They could also create a central repository of common legal clauses with easy to understand and reference names so if someone wanted to delve into the bitter details they could just read the name of the common law clause and already know what it means precisely because they've already read it before.
While it's true that adding additional text to a law can introduce ambiguity, I doubt adding strictly clarifying text will do so unless it's added by someone who's less than competent in which case they shouldn't serve another term in office. Unfortunately a democracy doesn't deal with incompetence that well since most of the voters are not intelligent and/or skilled in law enough to be able to judge a congressman's incompetence.
The only issue I see with forcing laws to be short is that some laws do in fact need to be long and complicated because what they are dealing with is large and complex, such as: the environment (which you mentioned earlier), aerospace (small mistakes kill people), transportation (mistakes kill people), interstate and international trade (macroeconomics is extremely complicated), etc.
I do like your idea of forcing someone to read each bill before congress and only allow those who were present during the reading to vote on it. It's an excellent incentive for them to write concise bills and to ensure that they have at least read the whole bill; although we'd need some way of monitoring whether congressman are actually paying attention. We could also require each congressman to summarize the bill before voting and if they don't show comprehension of the bill they must abstain. Or maybe require a quiz about randomly selected parts of the bill.