I know that not so deep in your mind, when you think about your own death, automatically comes a steady sensation that someway somehow clinical death is not the end. - John_Mann
I can honestly say I do not have that sensation. The possibility of a hereafter is more than a philosophical puzzle to me (metastatic currently in remission). I had no consciousness prior to my physical life, amazingly the world proceeded without me. It will do so again. I have had a general anaesthetic a few times. I suppose death will be exactly like that.
However I think this comment of yours is the real core of the debate. Unless life is eternal you find it hard to see that it is meaningful. Unless moral decisions are based in the character of an almighty god you see them as no more binding than a personal preference. You then make an unnecessary leap into abyss of nihilism.
I hope I have characterised your position accurately. Please correct me otherwise.
I do sympathise with your fears. Coming to terms with the provisional nature of our existence is not easy. The odds of our being here as individuals was astonishingly small. We won the biggest lottery imaginable the moment we were conceived. The speciality of our species was our large and complex brains, evolved for their ability to live in complex social groups using advanced language skills. We possess functions for empathy, compassion, justice and reciprocal altruism as well as guilt, disgust, fear, anger and revenge.
You make a distinction between Homo sapiens and the rest of the animal kingdom that is unwarranted. Ethologists have observed many of the functions that underpin our moral capacity in other species of social animals. Pre-human species left behind evidence that they were in any ways like us. They cared for their aged and sick and buried their dead with ritual. I could recommend some sources for you on that.
Christians build their beliefs about humanity on unproven and unscientific dogmas that have some very negative moral consequences. Prohibitions on stem cell research rests on an anti-scientific assertion about the zygote. Laws about contraception have done immeasurable harm to the poorest societies on earth. The desire for eternal rewards and justice leads to the indoctrination of children with disgusting threats about hellfire. Saving the souls of infidels from eternal torture has been the justification for appalling atrocities.
You seem to want to have your cake and eat it. You boast about the contribution Christianity has made to science and yet you want to put unscientific dogma off-limits. I found your assertion that "the logical conclusion of materialism is consciousness doesn't exists at all" to be especially strange. I have read Dan Dennett's book "Consciousness Explained" - he over-reaches in the title but nowhere does he claim the consciousness does not exist. Neither does Sam Harris. Neither have I. Consciousness is very real. However it is not necessary to posit a "ghost in the machine" in order to account for it.
I actually believe that theists and atheists find life to be meaningful for exactly the same ordinary reasons. Both of us have the similar longings and fears. Atheists accept the inevitable uncertainty, insecurity and injustice of life. Theists adopt evidence-free narratives that provide easy answers and go to extraordinary lengths to cover over the inconsistencies that result.
Lots more to say, but enough for now.