If you aren't doing abs heavy yet definitely get on that. Decline situps with a db and cable crunches are two good heavy ab movements. Pullups and/or wide grip pulldowns will help big time with width - heavy. For thickness I like to see various grips on seated row, with a good pause and squeeze on each rep and then an iso hold at the end of the set. If you're already doing tradition trap movements - heavy bb/db shrugs try something explosive like cleans or high pull. You'll certainly feel it the next day.
Lower back - are you deadlifting? Deads, good mornings, SLDLs will all help thicken up your spinal erectors. These all could be stronger than they look and you're just cutting yourself short with posing. If you have a bbing buddy or can find a guy/girl in the gym who competes I highly suggest you hit them up for a lesson. Anyway, you look good and you wouldn't look like a fool on stage.