sounds like your freehub body has well and truly given the bucket an almighty hoof down the street!!
remove the cassette and check it to see if there is excessive play, if there is then its time for a new one. i’m not too familiar with DT hubs but i’m pretty sure you can get replacements freehub bodies for them, any bike shop worht their salt would be able to advise you on this upon inspection. it might also be a good idea to change the cassette and chain if they show signs of excessive wear while everything is off.
if the hub can be repaired and the rim is still in good nick then you might as well stick with the wheel. you’re right it will be expensive to have a new hub built onto the rim, but again if you ask around at your LBS or look online there are plenty of bargains to be had on complete wheel deals.
as a rule of thumb a decent quality hub will cost between £50-100, spokes £10-20 depending on quality then you’ve got to factor your wheelbuilding cost which can be up to £20 per wheel.