You keep breaking spokes because there is not enough of them to support your weight. The constant cycling of tension/relaxing is causing stress at the J-bend.

Higher spoke tension would end the paperclip bending you are doing with every rotation of the wheel.

The trade-off of too high tension would be stress cracking at the nipples &/or the spoke bed.

Seriously. Just get a hand built wheel with 40 or 48, 12 gauge spokes and double wall construction like Velocity Atlas, Deep V, or Chukker and call it a day.

Related: You keep breaking the rear because the rear is where the weight is at & secondly you probably ride like a gorilla. (That's not a sleight on your weight. Some gorillas ride like feathers, some feathers ride like gorillas...It a statement of riding style.)