A buffer of 80 characters is: char buffer[80];
This creates 80 pointers: char *myData[80];
A pointer should point to something. In most cases they point to a piece of memory that you have reserved.
The characters are put in the buffer one by one with LoRa.read();
After that, the received text is in the array 'buffer'.
Then you still have to convert them to integers and float.
My example was just an alternative with a for-loop.
You can still use the String with the rc.toCharArray.
If you want, you can still create a buffer with: char buffer[buffer_len];
However, that is not recommended as was already written in Reply #11.
The LoRa.readString() that you used before does some waiting and keeps on reading until a timeout. That is not the best function, but there is for example LoRa.readBytes() which captures the data at once, but it does not add a zero-terminator.
Because of all of this, I thought it was a good idea to fall back to a basic simple for-loop to get the data.