Post a pic of that puppy!
I'm no expert, but have asked experts similar questions and have been growing mangoes for a while now.
15g is not very big for a mango root system, even if dwarf, when you consider fruit production. I would wait for fear of stunting growth or over stressing the tree. Nana reported a nice little crop on potted Pickering, and then 2 years with no fruit. Hard to say, but the crop of 1lb+ mangoes may have had an effect.
If allowed to hold fruit, would only keep 1 or 2, but not sure that is worth it. How good next year and the years after go may depend on what you decide.