With regard to the first, generally, improvement is to be encouraged. So, a student who started out with a D and ends up with a B on the last assignment should, overall, have a final grade that tends towards the B -- but, only insofar as there can be things found in the last assignment to justify a slight grade inflation.
With regard to the second, if students are taking an accelerated course (5 weeks vs. 10 weeks), then it's likely that there's only two or three assignments (instead of five or six). This means that early assignments will probably get disproportionately weighted. In a regular-length course, grades for early assignments will be weighted less than later ones, because it's expected that students take a little time to get into a course and really reach their actual level of ability. In an accelerated course, though, this is not possible because there are fewer assignments. So, to compensate, a little grade inflation on later assignments is necessary.
So, despite initial misgivings, overall I'm happy with how the grades turned out. I think those who deserved to be rewarded were rewarded deservedly, and the disproportionality was at least somewhat corrected for. And all this without sacrificing standards.