Are you staying on DVC points? Towel change on day 4 is only for those staying on points. If someone staying on points needs more towels, you have to pay for it. However, if you are paying cash for your reservation (not staying on points), you will receive daily housekeeping and towels like a normal hotel stay even if staying in a DVC room.
We stayed in a DVC studio and don't recall the bed being exceptionally hard to us, but we didn't sleep that great. I attributed it to being a queen size bed. We had just come from a Marriott in Kauai where we had a very comfortable king bed.