Yikes, Neal, if your house is at risk you'd better do something about those broken limbs (and check if the others are safe). No point in having the perfect flower beds if you're too squashed to enjoy them!!
I envy you your friable, rich soil. In France the soil is horribly sandy (in many places, just about pure sand) and in England it's mostly heavy clay... so one extreme to the other.
We have huge compost heaps in England, which helps but it doesn't seem to go very far. The older beds are not too bad -and for the past few years we've been using mineralised straw mulch against slugs and snails, so I guess that should eventually help too.
Not that I know what straw bale gardening is!!!