The continuation of the Carla scene there requires her to be pregnant.
I believe the Lin and Carla at the lake scene was just some poor coding (I should really stop coding at 4am) and will be fixed for the next release.
The Lisa challenge will require some help from Lin
As for Lisa, I think the part your missing is that you can get the altered note corruption. This will let you access her suitcase immediately without having to do the entire sidequest. Winning / Losing at poker is determined by whether you cheat.
Answering tit's requires about 8 head trauma or so
I'll investigate that last one