The rigging. A bit tough?

Am I the only one that feels that the chain shot is a bit feeble?

Especially lighter ships have real trouble disabling an opponents sail. While I have no beef with smaller gunned vessels having trouble shooting away a mast (those things are massive) even repeated salvos through the sails does very little to slow an enemy down. Even a full broadside of a frigate has little effect, needing repeated salvos to take the sail damage bar a single notch. And that's even with raking broadsides where shots go through multiple sails!
If you don't get lucky and bring down a mast you are just not going to impede movement to any noticeable degree.

Don't bother with broadsides. They are clunky, inaccurate, and FAW does a better job at damaging enemies.

I used broadside in the manner of all guns on a side able to fire, not the firing mode of ETW.

I've noticed the same thing. Multiple small ships attacking the same, larger target, seems to take out the rigging quicker.

Your guns all become synced if you use broadside once. There's no reason to do one manually after that.