He only needs a 5th place to seal it. If he finishes P6 or lower in a lackluster performance, he doesn't deserve WDC 3rd anyway..
Any position in the WDC is won or lost over a whole season not just because of one lackluster race. You get a whole season. Mclaren is in any case much, much faster then Lotus. If Lewis doesn't get the 3rd place then it is because his broke down to much, if Kimi loses his 3rd then it will be because the car in general wasn't competitive enough. One race does not make a whole season.