I’m taking your word on the 180 day count back math. You are correct that if you’re staying on site, once the 180 day window opens for your first day, you can book for your whole stay right away.
Word of advice… you’ll be in competition with everyone who is arriving in WDW on the same day, and y’all will be logging in at the same time… further (and worse), you’ll be picking from the leftovers of all those who’s stays overlap yours, but they’re staying longer and thus locked up many desirable spots days prior to your being able to make reservations, e.g. people going for a week, arriving on Sept. 30, and thus were able to start booking 2 days before you for the same period that you want. This is not to discourage you, but to lay down the narrative of why it’s really important to do this in a fast and efficient/effective manner.
Start backwards and work forwards, meaning book your ressies for the last day you’re at WDW first, as these will have the most availability. Do BOG first, then CRT, then everything else. Better yet, have multiple windows open and try to do at least two concurrently. You have a really good shot at CRT, but you should be prepared that all BOG ressies might already be wiped out. Don’t panic, just move on down your priority list. Over the coming days and months, check on the site frequently as people cancel their trips (and therefore dining ressies) all the time, so you may still get a shot.