Great job ... but I would still make some changes
Very nice job, and thank you for sharing! I have pretty much the same job in my close future (in a month or so).
There are two things that I am thinking about doing differently than you. One is to use epoxy all the way. I know it is more expensive than poly resin but with all the labor involved, I don't care if the materials are 20 bucks more or less, I want the best material, period.
The second is, instead of using one long strip of plywood, I am considering cutting it into several smaller pieces (not sure yet how small) and basically butt-end them with thin epoxy seams between them. This is for two reasons. First, as you emphasized, the deck is not flat as the plywood sheet which required you to do quite a bit of grinding and sanding. I hope to minimize this by using smaller pieces. Second, plywood is known to transport water along its grain. If, Heaven forbid, there is another water intrusion in the future(despite the counter measures you describe and that I will also adopt), I hope that it will then stop at the boundaries between the pieces.