its ok truemuslim
relax.
Your parents can be the biggest mercy for you and sometimes the biggest test. And it seems ur being tested, and do u no whom Allah tests. Those people he loves the most, the stronger ur imaan, the harder ur tests, take it as a compliment from Allah
Your dad seems like a lost soul, but make Dua for him, does he have a mother?, ask ur gran to make dua for him, a mothers Dua for her child works like magic!
STOP thinking these thoughts about the non existence of Allah! as soon as these thoughts enter ur mind, seek refuge in Allah from shaitaan, hes see ur a 'true muslim'! and hes completely jealous! lol.
remember how he sed to allah that he would encompass man from above him, below him, behind him, and infront, and becuse man is hollow he can defeat him? Are you going to let shaitaan defeat you?, think how much youve been thru, if u give up hope now, it would all have been in vain!
right now ur surrounded by ur grief and shaitaan is having a party becuase he can control u like a puppet.If u allow that, then you have let shaitaan win.
__________________