The fastest way to train for and break 6:00 in the 500y?

I've done 5 workouts so far this summer, and I think my 500 is around 6:50 right now, but that should drop quickly. I did a set of 12x100 recently on 1:30 and held around 1:25 on the last few. I think my 50 sprints are pretty weak too right now. I can only seem to hit 32-33, and barely hold 35s on a set of 5x50 on the 1:00. Should I do high yardage sets and get better at swimming slower longer? There exists a 100 pace that I can swim all day for miles and miles around 1:26-1:30, but once I get below, I tire easily. Or should I swim some harder 100s with rest as needed and try to shorten the base each workout? Or just try to build on a set of 100s on the 1:15 holding a pace