Is it the same distance taking 417 or 528 from the airport? Which is the shortest?
Taking 528 is closer, and cheaper, to get to Grande Vista. I'd estimate that the mileage from the parking garage - assuming that that's where you'll be picking up a rental car - is about 13 - 15 miles using 528 and 17 - 20 miles using 417. (variation is mileage depends on which side of the terminal - A or B - that you pick up your car and which side depends on which side your airline uses)
Also, from the parks to Marriott - you said take world drive. Are there signs to get to world drive? What signs do you follow out of the parks? Are you saying follow epcot signs exiting Mk or Ak?
World Drive is the main North-South road at Disney World. You take World Drive to get to the parking lot used for the Magic Kingdom and, going the other way, you'd take World Drive to Osceola Parkway to get to the Animal Kingdom park.
Going to the parks, once you turn from 536 onto Buena Vista Drive just follow the signs to the theme park that you're heading to. There are a lot of signs and they're very clear. I think that the best way to get back to Grande Vista from MK or AK is to follow the signs to Downtown Disney but the Epcot area resort signs (remember that it's the resort area signs not the signs for the Epcot theme park) will take you in the same direction (you pass the roads to those resort hotels on Buena Vista Drive when you go from World Drive to Downtown Disney and the entrance to 536 is on the right before you get to DTD).
How about Hollowood Studios to get back to 536?
Getting to Hollywood Studios or Epcot is pretty easy from SR 536. For Epcot just stay on 536 (which becomes Epcot Center Drive on Disney property) and that'll take you right to the parking lot. For Hollywood Studios, go from 536 to Buena Vista Drive (again there will be signs for the theme parks, etc.). The Hollywood Studios parking lot access is on the left shortly after the traffic light at the Victory Way (also on the left) intersection. So getting back to 536 is a right onto Buena Vista Drive and then a right onto 536 (signs for the airport, I-4, SR 536 and, I think, SR 417 just before the short right turn lane begins.
On all of this back and forth travel I'd suggest that getting from Grande Vista to the theme parks, and vis versa, via 536 is really easy and you'll be pros after one trip. Once you're on 536 just look for the excellent Disney signage after the I-4 interchange and you'll be fine.
Have fun.
Dick Taylor