Mate well done for being the responsible one and organising everything, hope it becomes less stressful and more manageable soon but you've been a hero mate.
Hard as it may be try not to be too hard on your family, if your sister is trying to help get her involved it will help you in the long run, we all make mistakes, let her make it up if she is trying. I would be fuming about the holiday too though.
Hope he gets better soon and it all gets sorted.
Keep venting on here if you need to mate, you got to let it out somewhere.