My father was a fun loving guy before he was an elder. Then he started walking around like he was carrying the weight of the world on his shoulders and he was never home. The best times we had were when we went on vacation and he didn't have to think about it for a few days.
I feel for you. I was a free spirit with an elder father too, and a mother who wanted to appear perfect all the time. It's a lot of unrealistic pressure. Someday you can escape. It's hard knowing how exactly to do it, and when, but it will happen. I think I've told you before, but get a part time job and save all your money. All of it. Use it later for college and living expenses because unless you have a rich sweet worldly grandmother you will need to do it yourself.
Edited to add: i love Pete's advice too, I think expressing this to your father may make your life a little easier for the present and may wake your father up a bit from his elder haze.