Hmmm, I wonder if you can supress teh weeds with cardboard or something? And try making a compost tea - have you heard of this? Comfrey is particularly good but alos nettle and broad leaf weeds, in water, allowed to rot, maybe with some worm poo? Layering the soil with mulch and organic matter in between seasons might help too. I can understand your frustration but you will get there in the end!