FMM Requirements - Free 7-day Visitation Visa?

We used CBX and flew out.on Volaris and back on Volaris.
Out stay was 10 days and we used the agent at CBX for our FMM form.
There was a fee we had to pay for over 7 days and it was expensive.

We are now leaving on Saturday for Zihuatanejo for 43 days and leaving from TJ through CBX.
We will have to have a FMM form filled out to get through security./customs.
Although this time we return back to San Francisco on Alaska.
In the past few years, when arriving into Zihuatanejo there were no FMM form requirement.
They stamped your passport with arrival date and put the departure date at 180 days after.

Since that is not goin to happen, I assume I will have to show the agent at Alaska counter my FMM card I received in Tijuana.

Rather than using CBX at airport to do this, I am going to try and fill out FMM form online and see if there is a charge that I have to pay doing it that way.