In the end, a payment of mBTC 3 will come to %btcaddress1%. But I want it will come in separate payments, and I want to pay a commission once.

In Bitcoin, you pay for each input you add in a transaction.
You can see how much you will pay here, to see if it is worth:
https://www.buybitcoinworldwide.com/fee-calculator/Before you ask what is an input.
Every time you receive bitcoin, it creates a new input. If you have one input in each address, you have 2 inputs.
Outputs are the number of destination addresses (usually one for "change" back to you and one for destination)
Your transaction will probably have 2 inputs and 2 output
I wanted to send a few payments of $ 0.5 but if sent separately the commission will make it unprofitable.
There is no commission in bitcoin network. Which wallet are you using? Just download Electrum (from electrum.org) and transfer all your funds there. You will make cheaper transactions and it will be profitable doing what you want if you use 1-3 sat/byte.