To try and answer some questions
In my opinion Carmen is hit and miss, I've had the same simple standing bid since day 1 and have a different roster every month-despite what my satisfaction score says.
If anyone fully understands the leave system they are not telling anyone. Captains struggle, as an FO I have got leave in 5 of the 6 summer months this year, but not Xmas. Less families etc I guess?
Leave is factored for PPY or part time
Doing other work during your off periods I believe is not clear cut and you need approval from the DFO, the official line is it can't be for a competitor, but I'm not allowed to exercise another type rating, just SFI,I'm full time though
If your only concern is getting to the LHS of a commercial jet as quick as possible, don't waste a sick day
Good luck