Hi and welcome to you and Hunter.
I haven't voted as not a real barf feeder [only a chicken wing now and again for a treat
Hopefully one of the barf feeders will come on and give you some help soon.
Hunter sounds like quite a chunky pupster at 11 kg already so looking forward to a picture when you get a chance.
I do agree about stopping the rice, for some it can be hard to digest,the little grains could be a sign of worms that have been expelled if the worming treatment has worked so I wouldn't be too worried about that.
I wonder if worms have caused the upset tum though, and also I would hope your vet has done a test on poo to see if there is any bacteria or Campylobacter infection causing runny and upset tummy as this would need treatment before you introduce anything new.
Good luck with the barf feeding when you have sorted poor boy out though, will be interested in hearing how you get on.
Oh and PICS' please