Take your time eating and enjoy leaving that night. It is magical leaving EPCOT when it is almost empty! (well mybe don't linger too long, servers need to sleep to!)
I've never eaten there before, but I usually make late ADR's and have never been rushed out of any of them. It's great to go late too because most people are already done with dinner and you may get the place to yourself depending on which restaurants.
I'd take my time with the meal - seeing as Illuminations goes off at 9pm, which lasts for about 15 minutes. Then the herds of people will make their way to the busses and monorail. Let them all go! You can relax with a nice Margarita for an after dinner drink, then head out after the crowds.
Well ordinarily I would say you'll be fine and made to feel welcome until you are through. However, SAI is really bad, particularly the service, so you never know.
I have never seen Epcot close at 9. The rides may stop, but they don't close. They always have Illuminations at 9 and we usually leave at 9:45. Has this changed, Illuminations earlier than 9?