Given your length, I outline so you can read selectively.

a. I don't define into existence, which would indeed be fallacy. I observe real things, compare things, and judge one to be the greatest thing, by scientific method. I then further observe this greatest thing. By that process I confirm all the core Christian truths listed in my link https://scored.co/c/Atheist/p/141reluACp/-burden-of-proof-is-on-the-one-m/c/4OUfR2Rkd1Q (thank you for asking specifically about them).

b. I quote Sagan because he used scientific method (observation) to determine meaningful definitions (nature of Cosmos). I think you haven't once engaged with these basic truths by affirming that things exist and that we can refer meaningfully to the sum of all being by a name such as Cosmos. I'm glad you recognize what it's like to be transitioning in belief, you'll need that.

You think I'm not a real Christian because I respect you enough not to overload you with detail (as in fact you asked) until you're ready. So here's the paths from basic panentheism to real, full Christianity:

1. "Jesus Christ as your savior": Most atheists agree Cosmos implies right and wrong and that they have done wrong. Reviewing all systems of righting wrongs, I've concluded Jesus's system ("salvation") is the best.

2. "heaven and hell": Recognizing the Cosmos contains consciousness, found in informatic selves (minds), I ask whether consciousness can be restored once lost by the self (resurrection). Both historical testimony and modern experience with millions of NDEs indicate so, so I've concluded everlasting destiny exists, and has at least two characters based on one's system of righting wrong.

3. "the Christian God": I proved the Cosmos was infinite (limitless); so I conclude the basic definition of Christian God by proving the Cosmos is also personal. Since I proved the Cosmos contains the sum of all consciousnesses (persons), the immediate conclusion is that it too has every characteristic of person, in which human persons subsist. The Cosmos, being limitless, also contains the unknown, so it's sufficiently transcendent to be identified with the Christian God (i.e. not impersonal panentheism but consistent with the other creeds).

4. "the bible as THE one and only authoritative source that Trumps everything else": I think so, but to prove this I would first define standards of authority, then determine which historical documents have authority for comparison, then realize the Bible has at least a high standard, then realize the Bible's statements if given a high standard demand instead an ultimate standard. That's outlined in my link.

5. "the label 'supernatural' on behalf of their God": "Supernatural" is not in the Bible, "miracle", "magic", "marvel", and "wonder" are. If these mean that which makes people marvel and wonder (the unexplained), good; if these mean nature contrary to nature, they would be contradictory. Again, C. S. Lewis, Miracles. I quibble about supernature because God cannot contradict his own nature; but if this quibble is accepted the word can then be used.

6. "the blood of Christ washing away your sins": Yes, that's Jesus's salvation all right. Blood proves commitment unto death, proving by the highest possible standard that Jesus's commitment to save was genuine and pure and his right to everlasting life was unimpeachable. Resurrection proves his power to share that life with us, purging our corruptions. Seems very reasonable given that atheists agree right and wrong exist.

7. "They don't make arguments where they equate god to the universe or a force of nature": They do, but they don't ignore his personhood either. I respect you enough not to overwhelm you with personhood while we deal with other attributes. Christians say God is All Being, not just the (observable) universe, but the whole (known and unknown system) Cosmos: his name is "I Am", implying All Being, personally. Christians say God is many impersonal things, Light, Love, Spirit, Way. "Force" is not used this way Biblically, but Power and Authority are, Energy is used in Orthodoxy the same way, and LORD of Hosts means "I Am of Forces". So when theologians inquire in colloquy with atheists, they agree with atheists that "In him we live, and move, and have our being" (Acts 17:28 quoting Epimenides, also Aratus).

I did have minor "grief" or "anger" on realizing my parents' system of Christianity, while sufficient, was incomplete. I "accepted" losing the imperfections because of the much greater joy on finding further completions and on anticipating the process continuing forever. That's scientific method. I did choose Christianity:

belief is not voluntary. You never chose to be a Christian.

If true, you admit you might become a Christian without any choice; great! If false, you would need to accept the responsibility of choice and investigate both your former faith and the attack that removed certain illusions from it but left you to doubt the solid part of it. Just because you recognized that your original system was imperfect doesn't mean the system needs total discarding: rather, the scientific method is that we refine theories and surgically remove imperfections by greater observation and experiment. In this, I don't wish people luck, I wish you blessing. You're free to share about "trying to cling to something [what thing?] you know [how?] isn't true".

personally I like Christianity (real Christianity not fake internet Diest-christianity) and think it's a force for good in the world