Hi,
Welcome to the forum !
Being in Australia, your season is almost over ... or not ?
Funny how the container in the pics looks so small. 20''/50cm in width ... Doesn't look like that, but like half of that. Funny.
I would pot that tree up.
The tree having such a thin trunk ... I would call that a tissue-cultured tree. Those can take some time to fruit. 3 years and more.
So be patient, and take good care of her. Once mature enough, she will fruit.
As for trimming, if you expect fruits, just do it once a year, or every other year.
The 3-2-2 will do for fertilizing.
As for the size of the pot, between 4 and 10 gallons ( +water+fertilizer ) would help for better production . You can have them in smaller pots, but then you have to monitor more closely watering and fertilizing.
It will take some time for the tree to show lacking of something, and then even more to catch up, and that'll shorten the growing period.
Good luck !