I will try not to make this complicated. If you look at
Ultramar you can see the ferry schedule. It alternates with
Mexico Water Jets So between them, ONE them is running at all of those times.
Then there is the new ferry,
Barcos Caribe. But basically Barcos leaves Playa Del Carmen last at 11pm and one of the other two leaves Cozumel at 0600.
Figure 50 minutes in the crossing. 50 minutes on a van between Playa and CUN. You could be in the check in line by 0800.
Mayair leave Coz at 0700, 20 minute flight so you can be in the check in line around 730 ish. You can negotiate a little better price than what is on the website if you call or email them.
Basically early morning departures can be tricky. With the new 11 pm ferry late arrivals are pretty doable.
I will PM all my van guy stuff.