sprocket design for custom cyclone motor ebike

I have a custom made cyclone motor ebike using motorcycle #428 chain sprockets. My current setup is powering the motor from a 24v li-ion battery pack but I am planning to upgrade the battery pack to 48v as the motor can handle 24v-72v input at 3000watt.

I have a 14T cog on the motor shaft and I have (2) 49T chainrings. One is connected to the 14T cog on the motor shaft while the other is connected to a 13T cog/sprocket on the bicycle hub at the back. I have good speed on the flat but my hill climbing ability is very poor at 24v.

Which teeth size sprocket would be more suitable to put at the back? so I have good speed on the flat and excellent hill climbing ability at the now 24v that I am using and also whenever I upgrade to 48v that same sprocket would be also suitable too. If not then suggest one for my current 24v setup and one to use with my 48v setup in the future.

You can take a look at this link below and make the suggestions for me please.
https://www.aliexpress.com/item/4001135754551.html

Is this the kit you have?

https://www.cyclone-tw.com/product/6/data/27

If so, what wattage did you get?

How fast do you go on the flats?

https://www.cyclone-tw.com/product/6/data/17

That is the kit i have above 24v-72v 3000watt
But I modified it and used motor cycle bike #428 chain at the front and the back.
I get about 20mph on the flat.
I want to change the 13T sprocket at the back to one that gives good climbing and good speed.
I have (2) 49T chainrings. one is connected to the 14t cog on the motor while the other is connected to the 13t at the back.

Would changing the 13T at the back to a 28T would be a good ratio for climbing steep hills and still close to the top speed that I have now?

What is your tire diameter?

How many max continuous amps for the battery? How many burst amps for the battery?

My tire size is 24". My continuous amps is between 17-20amp on the flat and my burst amp is around 31amps sometimes as much as 34amp. My amps going up a hill is between 28-30amps, mostly 30amps drawing constantly due to the fact that the controller limit is 30.

The max constant amp rating for the battery pack is 30amp.

I'm currently using a 28T sprocket on the back and the same 28T on the motor. My amps draw on flat terrain is between 28-30 amps. I want to decrease my amps draw on flat terrain to about 20amps max.

What ratio would be best in terms of teeth difference to use. I want to keep the 28T at the motor shaft so what size sprocket should I use at the back? The options at the back are 32,34 and 38.
Which one of these would be best to use at the back to get that 20amps max draw on a flat terrain with good enough torque and a speed on flat terrain at 20-25mph?