Shrug. I mean I like dips, and push over 100 lbs so my triceps are pretty strong. Both will get you there though..
Abs are worked in the hanging knee raise... and as stabilizers for pretty much all the other exercises. You don't need any extra work for now.
The pendlay (?) rows in SS are the sub for the pullups.
I know for Bill Starr's 5x5 you're supposed to do the ladder of increasing weight. With SS IIRC you're supposed to add 5-10 lbs to ALL of your 3 work sets of 5. So if your work set was 225 squat last workout, it would be 230/235 squat for 3x5 next workout.