You are confusing parameters with quantity of transactions, a parameter is information passed to a command, if you look at the api reference for bitcoin you will see that you have to submit parameters with the command (up to 8 for the sendmany option) so the number of parameters is static, it is the quantity of entries inside of each parameter that changes.
Looking through the api reference (https://bitcoin.org/en/developer-refere ... -core-apis) it would seem like you could use the SendToAddress to send an individual transaction, and it looks like it might be simpler to build the command. To do this you would read each line from your file and build the command from that one line, send it (using SendToAddress and then move to the next line etc, etc, etc...