Retail using POS - Item price with non fix cost (random)?

My store is a Pharmacy and I have another software that calculates the prescription drugs amount, and where I live, people have various different insurance and the pharmacy software can print out a receipt of the amount for the patient left to pay after insurance. There is no pattern in price, as it can vary from 0.01$ to 9999$. Therefore, no price list for the item is possible.

At the cash (POS in erp), we need to manually input the prescription (as a service, no stock maintain) and I create an item called Rx. I need to manually edit the rate of this item for every prescription.

But here comes 2 problems:

1- POS will automatically save the rate (price) when I change the rate, so I always have to delete the amount for the next client.
2- If the patient has more than 1 prescription, pressing the item Rx will update quantity and set the same rate as earlier. Which makes it impossible to have 2 Rx at 2 different amounts on the same transaction. I would like to avoid having max one rx amount for each transaction and having to manually calculate the sum of the prescriptions to put as one (because it increase human errors as it is manually calculated)

Here are my other questions:
A. Is there a way to solve these issues?
B. Does pos awesome allow us to solve this issue?
C. Can the price rule be helpful in this situation and if yes, how do I set the price rule?

My current workaround:

In Rx price list item, I set the unit of measure as $ and have a factor of 1, and item rate is 1$.
Instead of changing the rate in the pos, I change the quantity. So a prescription of 55.14$, i put quantity as 55.14 and grand total gives me 55.14$ (as quantity of 1 = 1$ rate). But doing this, it will give me a wrong report of how many Rx I sold.

The 2nd question, I have to create a new item with Rx2 to input in the same transaction, and Rx3 to have 3, Rx 4 to have 4…