On a useful note, have you tried creatine? Outside of improving technique, this is the only change I've made in my rather unimpressive stab at the Program and my performance has become much more consistent than in the past.
On a less useful note, more qualified people than myself will respond, but I've read this forum long enough to have opinions
, so here's a sample:
1. Unless you are interested in a "burnout, recover, re-evaluate" cycles that last weeks, I'd pick my goals and find an existing program that matches them. There are a few on the SS Programming forum. Outside of a variant of SS, 5/3/1 is a popular choice. General Programming forum would be a better place to ask about it. For SS-like program that compliments Judo,
this is a sensible program, I hear.
2. Being bad at a good exercise is not a valid reason to add it to your program. There's a tonne of those, getting good at them will require as much focus as the main lifts did but adding them will take away from progress in the big four. Starting Strength incorporates two: chins/pull-ups and power cleans. You're already doing chins, so maybe it's time for power cleans. Coincidently, they are a lot more dynamic than the other exercises, so may provide a sufficient endurance fix.