I'm really sorry to hear about this. I've had at least a dozen friends commit suicide, most of them were practicing witnesses. In fact, some years ago, my girlfriend committed suicide after having been "disciplined" by elders for alcohol abuse. Admittedly, she had a lot of problems, but who doesn't. They, in fact, announced her name in one of those "discipline" announcements from the platform. This, I'm still having trouble trying to figure out, since having served as an elder for about 10 years, I know that the Society's guidelines are pretty clear as to when these kind of announcements should be made. Interestingly, in her congregation, about 6 other youths took their own lives within a 3-year period. Of course, Society teachings and the subsequent congregational peer-pressures are what is causing undue stress upon the brothers; I don't see this changing any time soon.
One thing to remember my friend, is that there was likely nothing you could have done or should have done to prevent this outcome. Anyway, God is very tender in compassion and won't forget your father in the future resurrection. Meantime, I'm like you, trying to pick up the pieces from having been mislead in believing that God's promises will come sooner rather than later. However, do let up on praying to God. He does listen and respond to our concerns and is way beyond any human or religious institution.