Try a larger size seems the sensible approach.

I do stay off peoples lawn chairs tho'.
I stick to picnic table benches if they have them.
I did squeeze my big ass into a wooden rocker at Cracker Barrel and it held just fine.

I have gotten used to chairs and couches creaking when I sit on them.

A persons health comes before your personal fetish.

I broke a wooden lawn chair once.
I was 425 at the time.

Sounds a little one sided to me.
I think you need to make your concerns known to him.
Sweetoothsweeheart makes a lot of sense.

Thanks Skinny boy.
I just comment on what I know and have experienced thru out my own life, other people may have experienced it differently so their points are valid too.

Think of of it this way you don't tell others what to do in their life so why should they feel they can tell you ?
At 18 peer pressure is a huge thing and every thing revolves around friends but as you mature you start to think more for yourself and their opinions don't matter so much.

MottiF makes some great points.
You are living for you not someone else.
Parents will always stick their nose in anything you do until you are out on your own so if you live under their roof its their rules for now but that doesn't mean what you eat when you are not at home.