Any suggestions on how much sugar syrup you should use that would be a close substitute? I cannot get access to sugar cane juice, I used 10ml of 2:1 but I feel it was a bit too much.

I don’t think cane syrup requires you to process sugarcane, it means syrup made from unbleached cane sugar which you can buy at a grocery store. Since it doesn’t specify rich syrup, I would use a 1:1 ratio. This might account for the extra sweetness you experienced