1. According to TouringPlans.com there are 30,469 on-site rooms, and 60,685 off-site rooms. Those numbers are published (WDW does say how many rooms each resort has, you just need to add them up).
http://touringplans.com/walt-disney-world/hotels/number-rooms#
So by that measurement, the number of rooms on-site represents 33% of total rooms in the area.
Also, TEA's attendance numbers give 19,332,000 for MK, 11,454,000 for Epcot, 10,402,000 for AK, and 10,312,000 for DHS. Add them up: 51,500,000 for the year, divide by 365 = 141,096 people per day entering a theme park. If you assume 100% room occupancy, and 3 people per room, that equals 91,407 people onsite. That equals 64.8% of people being onsite. If you assume 90% hotel occupancy (27422 rooms), and 3 people per room, that equals 58.3%.
So somewhere between 33-60% But people have non-theme park days, non-Disney days, some people are on business trips (conventions), some are couples, some have large families. For convenience, I assume it's about 50%.
2. In statements made in early 2014, after the rollout of MyMagic+ to all guests. Bob Iger, Jay Rasulo and Tom Staggs would say that with legacy FP even after 10 years, only about half of visitors were using fastpass. And I think it was in a CM communication, that George Kalogridis said something like 2/3rds of on-site guests were using " advance My Magic Planning Tools." But there was no discussion about which tools they were using? Fastpass, dining reservations, simply looking up hours? Or when the time frame of usage was. Big difference between using tools more than 180 days, or more than 60 days before your trip versus the week or day before. I would guess there is a spike at 60 days, a spike at 30 days, and another spike within the last week, and a significant of guests don't do anything until they arrive. But percentages? I would guess that maybe 60% have at least 1 FP day. More people probably have DHS as a FP day than AK.
3. The DIS forum front page says there are 478,587 members. That's since the beginning of DIStime which was like May 2001, so there are a lot of accounts not being used anymore, 2nd accounts, etc. So maybe 100,000 people actively planning a vacation, so maybe 500,000 including all their friends and family they share with. 7 day vacations, so maybe 3.5 million vacation days out of 51.5 million or about 7%.
But here's the thing. 7DMT has like 1800 people per hour capacity. Over 12 hours, that's 21,600 people. Average MK attendance is 52,964 people. If 10% are heavy planners, that's 5296 people. That's 24.5% of 7DMT's daily capacity. Then you potentially have 47,668 fighting for 16,304 seats. Or basically 3 people for every remaining seat. And that's not even accounting for people who want to ride more than once. People like to say that others just need to "plan more." But the more heavy planners there are, the faster available seats disappear. If 25% of guests were heavy planners, that would mean 13,241 guests in the MK on a given day, and that's now 61.3% of 7DMT's capacity. Now, if you have something like a restaurant which can only serve maybe 150 people per seating and maybe only 4 seatings, you can see how even a small percentage of heavy planners can overwhelm a facility.
