family member of EU citizen , child over 21

my dad is EU member and he is exercising his treaty rights as self sufficient and have a health insurance, my question is how can i apply under child over 21 ? i know i need to show i am depandant on him financially , but im working part time and another question is how can we show he is not out ot uk for more than 6 months?? when he comes in or when he goes out there is no stamp in his passport how can we show that he is here for 6 months in each year ?
plz helppppppppp

Please continue in your previous topic.