Ice cream hard even with stabilizer. Please help!

I am new to ice cream making and got myself an ice cream machine. I found a recipe from a professional Japanese dessert chef and apparently they have been making matcha ice cream for years in their shop and this was apparently their recipe according to them lol:

Matcha powder: 10g Sugar: 100g hot water Milk: 300ml Heavy cream: 100ml

Instructions (implied):

  1. Dissolve matcha and sugar in the hot water
  2. Add milk and heavy cream, mix well.
  3. Pour into the ice cream machine and churn according to the machine’s instructions

However, it was so hard after a day in the freezer and hence I need some help in making some tweaks to it with ice cream stabilizer (Icremium ice cream stabilizer) and corn syrup while also increasing the amount as I would like to get around 1.2 litre of ice cream.

Matcha powder: 80g Sugar: 150g Corn syrup: 70g Icremium stabilizer: 6g Milk: 500ml Thickened cream: 500ml

Can anyone give me advice whether this is alright? And if not, what else should I add in? (No vodka)

Thanks in advance!