@racereer - thanks for the detailed info.
Its similar at sons school - 5 for an A in AP (an additional .2bump for A+); think for honors its 4.5 for an A. So theoretical max in the school is 5.2 but since there are restriction on when and how many AP’s they can take the practical max is 5.0. School does +/- to the letter grades with some additional bump for A+. Son has 4.85 W and 3.83 UW - I think the discrepancy for his W/UW and your sons maybe because of +/- and since DS did really well in AP courses (especially math/science A+'s) but so-so in some honors classes. With add-on bump for A+ in AP courses he got better W. Fortunately, school ranks based on W and reports only W on their official transcript. But I heard colleges may recalculate with no +/- (?) in which case it will be 3.8UW.
In terms of course rigor, he took 13 in-class AP courses (by end of senior year) + an additional 2 self studied AP tests (those 2 courses are not offered in the school).
Its true that his GPA may not change much after first semester - the main hope is on his Multivariable calculus (results are out by Dec 15th - he is doing so far well - knock on wood). Plus the research he is doing with a prof could be in better shape by end of Dec. Hope is that they both can give a wee bit of a boost. This is all my (wishful) thinking 
- end of the day he will be applying to all the colleges above either in EA or RD. Just dont want him get rejected outright in EA because of couple bad grades in junior year.