Incoming wall of text...
From someone that similarly left Christianity around the age of 19, I can empathize with a lot of your feelings here. Was raised southern baptist and it took a long time of thinking critically about my own beliefs before I similarly drew a line in what behavior I was willing to accept from a "benevolence and almighty" god. I eventually stopped just blindly accepting "God is great" statements and decided to really think about the sorts of things he did in various stories in the bible, as well as examining the more primary concepts of Christianity(original sin(being a form of guilt that was somehow passed from parent to child), the idea of a binary reward system that arbitrarily punished people that had never even been exposed to Christianity, just because they'd failed to get baptized, and the nonsense declarations of morality that are ubiquitous throughout the bible(Leviticus style forbidden acts such as mixing fabrics or eating certain creatures, all the way to the establishment of a thought-crime in the 10 commandments(coveting neighbor's possessions(farm, pigs, wife, etc))).
After hitting the point where I determined that I wanted to shed the veil of ignorance that religion had cast over me, I started to apply this new mindset whenever I came into a situation or train of thought I had previously resolved through religious beliefs. I recognize some of the thoughts you mention, and maybe it would help to know how I ended up coming to terms with these things?
As far as the fear of inevitable death, and the really transient nature of our existence(individually, and likely as a species); I think the sort of insights that help to calm this anxiety tended to come from other people. I listened to a lot of youtube videos of modern Atheist(or non-religious) speakers(Christopher Hitchens, Richard Dawkins, Sam Harris, Daniel Dennett, and Neil deGrasse Tyson). A few things that stood out: deGrasse Tyson talking in his ever-passionate manner about how we are all literally made of star-dust and how he would prefer to be buried in some manner so that the creatures of the earth can reclaim the nutrients of his body(his way of giving back his body to the planet that birthed him)(entirely possibly that I'm misquoting him in some manner), Richard Dawkins speaking about the process of evolution, which obviously still enthralls him even after all these years, or Sam Harris's thoughts on post-religion morality(see his book The Moral Landscape). These sort of things really helped me to get past the fearful thoughts of death that I've experienced occasionally throughout my life. I will warn you though, I don't think that many people ever fully quell those fears, so expect them to pop up at various points in your life as you sort of reevaluate things repeatedly.
A more common argument I see put forth by religious people to rationalize their belief without actually arguing that the bible is factual is to toss out the old "religion gives people(esp older ones) peace of mind" bit. I have a great-grandmother(somewhere around 94 years old) that is very religious. She listens to preachers on TV because she is no longer mobile enough to attend church in person. I initial just accepted that maybe Christianity was a positive thing for her as it allowed her to avoid the more morbid realities of her impending death, the death of her husband two decades ago, the death of her younger brother at a very early age, and the countless deaths she has had to endure over her very long life. Eventually though, I started to catch glimpses of the negative consequences of her beliefs creeping out in my occasional visits with her. She would consistently ask me if I had a girlfriend. I thought it was innocent, but realized at some point that she was trying to positively determine that I was straight, as if she thought I was homosexual, she was certain that I would spend an eternity in hell. This fear at e at her so much that she asked me if I had a girlfriend every single time I saw her. Eventually, she became more blunt and began to ask if I ever went to church, and when I said no, she asked if I would go to church for her sake. I'd offer her some very vague lines, like "I'll consider it", but never really told her the truth that I never intended on returning to church because I know the sort of pain that sort of truth would cause her.
I think this particular realization that her thinking was so insidiously clouded by the nonsense that TV preachers fed her really hit hardest when I played her a Spanish-style guitar piece that I was extremely fond of on a classical guitar I had just bought. I adore the piece, and since nobody in her family had ever really played an instrument for her before, I imagined that she would get some modicum of enjoyment out of it. Instead, after I finished(or maybe while I was still playing) she simply asked if I knew any church music. Her thinking has been directed in such a manner by her irrational beliefs that she can't even enjoy her great-grandson playing music for her without some kind of guilt arising due to the secular nature of the piece. Frankly, her reaction disturbed me, and it really drove home the way religion really can twist someone's mind while simultaneously convincing them that it's offering them the only real hope/enjoyment there is to be had in this world.
Hopefully some of these thoughts can help you on your path to gradually reclaiming every last bit of your mind from the indoctrination that so many of us experienced in our youth.