I had spoke issues earlier this year too. I am 250 lbs and usually ride with two panniers on the rear rack jammed with work stuff. After having the telltale brake rubbing cancel one too many commutes into work, I took my rear wheel in to a local bike repair shop with a good reputation for wheelbuilding. For $70, he rebuilt the wheel with better spokes. I took it back in for retensioning once after a spoke got a little loose, and he readjusted for free. No other problems in 500 miles since, for what it is worth.

If you like the bike but hate the rear wheel durability, it's worth having the wheel rebuilt by a good bicycle repairman. Could solve your problems.

At some point I will probably get into wheelbuilding myself, to be more self-sufficient. For now, I am racking up the miles and learning about commuting in my first year living "car light."