Mmm, I see what you mean. Actually I've heard that the laugh reflex is not uncommon, because as you say it is a demonstration of emotion, even if it's not really appropriate.

I'd still give this person a second chance, but if you are as mad as you sound, definitely make your feelings heard (though perhaps start moderately, as there is still a chance your friend doesn't know how to react).

Careful about saying things like "no one ever supports me". I'm not saying it's not true - I do know the feeling - but what I mean is that don't let such thoughts eat you up, as they so often can. Talk to a T or someone else if you feel yourself in a spiral.

I meant to offer best wishes to you and your father as well. My Dad had double bypass surgery a few years back...not as hard to deal with as cancer, but still some pretty hard and hectic times. Good luck.