If you ask 100 guys who grow bonsai what kind of dirt to use, you can reasonably expect to get 110 answers.
Acer palmatum grows pretty strongly in pots. I would expect you are going to need to remove a portion of the soil every other year.
All trees do better with very fast draining soil with about half being coarse stone. I use layer or turkey granite grit from the farm feed store. Its affordable and mostly does not need to be sifted.
A tree will grow in soil with a fine particle size, in your yard. In a pot it needs more access to air. Forget that and you will ever be battling (and loosing at) root rot.
I get less critter damage in the winter with osmocoat pellets than organic fertilizers. Four legged critters go where their nose takes them.
