Where can I find miso paste and tamari?
@Asia Market sells miso paste and several sauces (never checked for Tamari though)
Where can I find dulce la leche spread?
might as well make it yourself in the oven or in a pot of boiling water.
Where can I find wireless mouse for my laptop?
You could also try either branch of @GTS - Glory For Technology Services or any other shop in Gardens street.
Where can I buy instrument equipment excluding freddie for music?
if you can handle used instruments then I'd recommend trying your luck on Facebook groups especially "musical instruments for sale in Jordan". You'll get a better range than most shops. @MKK Instruments Custom Shop also does quality work.
Where can I find ergonomic mouse?
Try Gardens street (especially @GTS - Glory For Technology Services but also loads of other places). I'd recommend spending on a good brand like Logitech G or Corsair though. Avoid no-name brands.
Where can I find the most delicious sushi?
@Noodasia is pretty cheap when they have All You Can Eat. It's just not that good tbh.
Where can I go for all you can eat sushi (include price if you know)?
@Noodasia has decent all you can eat sushi but I'd honestly go for something nicer personally.
Where can I buy molasses or dark corn syrup?
@Virgin Megastore has molasses and treacle. @Fouad Supermarket has molasses.