a) you feed about 2-3% of adult weight in meat and bones. Any veg you feed (some feed a lot of veg, others none - it depends what works for you and your dog!) is on top of this.
Honey gets a breakfast of between 80-150g (depends what it is... she's less willing to eat pork ribs than chicken wings!) and an evening meal of about 120g.... she also gets kongs with tripe filling and the occassional egg treat....
b) I don't find it hugely expensive - if you can find a helpful butcher it can be even cheaper!! We get most of our food from the supermarket, but as it's the cheaper bits of meat, it's not too bad (we buy lamb bones from morrisons, pork ribs (prob the most expensive part!), chicken wings, lamb heart, ox heart, lamb liver and then we get tripe from the pet shop....).
c) As we feed human quality food, the risk from worms is minimal - we worm every 3 months (though considering going up to monthly for other reasons....) - vet is happy with this. Freezing meat (and then defrosting) before feeding reduces the risk of worms further!