As far as the discounts, your guess is as good as mine. That's why I started the post with a preface that I received all the offers based on one trip only. There is also post covid need to fill up the ship to consider. Having said that, each offer (they sent through email or snail mail) are valid for 3 trips, but the free play only for one. For example if you are sent an offer of free inside stateroom + $100 freeplay, you can use the free inside stateroom for 3 different sailing, but you will only get the $100 freeplay for the first one. So, if I have more time, I would have been in ship a lot more often since I received at least 10 offers from Princess alone.
As for clawback, I doubt they will do that prior to your journey. Now, if I go on all those cruises and I don't play at all, then yes. They will definitely cut down the amount of their offer. Having said that, I don't have to play at all the cruises either, especially since European cruises tend to be very port heavy. My budget is always not to exceed whatever the market price different.
There is also the "standard" discount from simply being casino player in Holland America. I believe it's $200 per person for the first 2 occupant. It is offered randomly depends on ship availability.
Last, yes the $1300 is basically what shown on my room statement. It's the amount of money I put inside the machine, not the total play. Your comp is actually based on how much money you play, not how much money you put in. That's why they don't care whether you win or loose, you will still get the comp if your play is high enough. Their purpose is not to make you loose because the more time you spend on casino, the higher the chance you will loose. They don't have to make extra effort on that, it's built into the system.