I'm going to chip in here on what seems to be the (vast) majority side here. Yes, the story could be shorter - of course it could. You could have written the whole lot as a short story and been done with it. But it's not a short story so the style is that of a novel.
How many chapters could you have saved with a sentence along the lines of, "After leaving the Suez Canal, Trevor was set upon by pirates and was lucky to survive, eventually limping into Carnarvon under a jury rig, having lost what little was left by the pirates during a storm in the Southern Ocean"? A dozen? More? Would it have been half so good a story? Of course not - not close to half. A fraction too small to measure probably.
You mention the Kline/Fowler interview specifically. You could simply have said that they came to an agreement for Kline to publish a version of the story tailored to remove any specific references to Trevor's whereabouts. It would have got the message across. We'd have known why Fowler was picking Kline up and taking him out in the Coastguard boat. I for one, though, would have missed it. I want to be there for every detail of this story. Trevor and Shane are friends of mine now and I want to know exactly what's going on with them. I really hope we see some more of their explorations as Shane takes on Joel's role as Trevor's travelling companion.
Too many characters? I confess, I'd forgotten all about Ben, but I do know what Atlantis looks like so he served his purpose. I could tell you a fair amount about all the main characters - I really don't see how you could have many fewer. There just aren't too many - I don't think the average reader can be having that much trouble.
I think you have a point when you point to the serial nature of the story, but it's not the point you're talking about. It's not that it's become bloated it's just that we all have to wait a week between chapters so, of course, it seems longer. I came in somewhere near the end of the Southern Ocean I think and I can assure you that there was never any chance of me not going directly from the end of one chapter to the start of the next. I'm pretty sure that if I were to re-read the whole thing then that feeling would continue right up to the latest chapter.
One day, you may publish this story in some other form. I'm not a literary editor or anything but, one day, I'd be happy to part with cash for a paper copy of this in a bookshop. Maybe then, some editing will be required, but I hope you don't mess about with the timeline too much. I suppose Matt Damon will be too old to play Trevor by the time the film version is made...
So, let's have the 4 chapters that are with your team as they are. It is, of course, up to you how you write the following chapters, but I hope you won't be tempted to shorten them too much.