The fixed legs problem has been discussed several times on the forum, and it's a result of an FSX optimization that turns off all animations after a certain distance, so it can be usually fixed by going closer to the airplane.
Disappearing people are usually a problem with video card settings or FSX settings.
Try to reset your video drivers to default and, if that doesn't work, reset your FSX.CFG to default settings by removing (or moving to a different folder) the %APPDATA%\Microsoft\FSX.CFG file and be sure you apply at least the HIGHMEMFIX = 1 Tweak in the Addon Manager.