Welcome Aboard!
It is possible to sink a plane with a torp.
As for "sympathetic" damage - this does occur in the game - as well as it has happened in RL.
I have only seen it twice in game - and both were during a test. I set every zone on a bb to hold ammo, then placed it right beside a DD. The BB screened the dd from me, i hit the bb with a torp - she went up like a rocket - and the explosions of all the ammo took out the adjacent destroyer! The second test - I set my torp to nuke warhead strength(5000 damage - area 2000) and everything toasted!
In history - at Pearl a warship sunk when a torpedo exploded on the hull of another ship. Her seams let go and down she went....