Stative verbs are internal "actions", such as want, need and love. To put it simply, if you can see the action (such as standing or sitting or lying), then it's a dynamic verb. "Stand" is definitely a dynamic verb. :) "He is standing up" means a movement from a sitting position to a standing position. "He is standing there" is the action we can see at this moment. Then, we can say "he is waiting for the bus", but "he wants to get to work on time".

Yes, standing and sitting are dynamic verbs, because they are actual actions. Remember your photo of the fellow on a wooden terrace in a smart coat? He is standing, he is smiling, he is posing for a photo, he is wearing a coat, he is breathing, he is looking at the photographer, he is thinking about his girlfriend, etc.... all of these things are dynamic verbs because they are actions happening at the moment. To work out the difference between stative and dynamic verbs, it's sometimes useful to compare different meanings of the same verb. For example, verbs to describe the senses: "Lemons taste sour" - This is a stative use of the verb, because it describes a fact. You could never use this verb in a continuous form when it has this meaning. "I'm just tasting the soup before I serve it, to see if it needs more salt" - This is a dynamic use of the verb, because it is an action. This is why you can use continuous form here.