Plums can have a very thin layer of wax on the outside.
This wax will make the wine cloudy.
I always wash the plums in handwarm water with some soda to
get rid of the wax. I do not suppose you did this ???
It is a bit of a pain to handle plums (I had 200 kilo's this year again), but plum wine can be worth the effort.
(look at my web-log in the archive at the 22 july entry :
http://wijnmaker.web-log.nl/wijn_weblog/2007/07/22/index.html).
What yeast did you use ?
The yeast flavor will disappear with aging. This wine is from September so still very young !!! You need to have patience.
Wait if the cloudiness will fall out, it will take some months.
Putting the wine in the cold (it is freezing here in the Netherlands at nights) will cold stabilise the wine and will help clearing.
To sweeten it, wait until it is ready and then add sorbate and sulphite and then sweeten.
Luc