Ok, so first of all, I should probably start off by saying that my worldview doesn't always overlap with Christian belief, which would disqualify me from being a Christian (as you could have already guessed based on my posts). Nevertheless, I strongly believe that there is a Creator.
For example, I don't believe that God told the Israelites to kill all those tribes (sometimes including women and children), I simply refuse that God would command such a thing. But still, if someone reaches enlightenment through Christianity or if it helps him become a better person, I respect it (but I would also respect it for other religions as well).
Now, regarding Jesus. Obviously, we don't have a video of someone from 2000 years ago. What we do have is written accounts from people who saw him. You might say that it isn't enough, but that is pretty much how we know about any historical person who lived a long time ago. I also don't believe that a whole religion that most people today follow would come out of text made by a person who decided to make up a character named Jesus that never existed. Note that in reality, it wasn't even just one writing, but there were dozens of gospels about Jesus (but only 4 were included in the Bible).
Regarding many miracles in the bible - I believe human thought and its power to create images has great potential - especially (and this is important) when it taps into some divine energy which multiplies it many times. However, that knowledge today has been lost. Think of how if you told a caveman from 20000 years ago that one day there would be modern technology, AI, rockets, spaceships, etc., he would probably just mock you, as all they currently have are spears, bows, and javelins. People today are very much like 'cavemen' when it comes to the power of what we can do in that aspect.
edit: forgot to address this:
This one is the easiest, the world itself is the creation - it must have the Creator. I find it absurd to think that the universe, as complex as it is, would just form on its own.
your issue is the killing of canaanites, the ones sacrificing their children to molech, regularly committing bestiality, incest and other evil acts? they were patiently given hundreds of years to change, yet refused to. should we not have a righteous judgement on debauchery, crime, and immorality or continue to act this way forever?
not the flood that killed way more, did that not have a bigger impact on you?
is your issue that He used a particular group of people at a particular time to enact His judgement rather than an act of nature? this was to enact the correct way of being to humanity, to teach the israelites the correct moral way and ultimately to have His Son incarnate and teach the world the gospel, giving way to restore the human nature ontologically back to its true nature via theosis.
if He allowed the complete debauchery to exist, the Israelites would be corrupted (as they were later, because they actually didn't follow his commands). The point was "so that they may not teach you to do according to all their detestable things which they have done for their gods, so that you would sin against the Lord your God".
you find it absurd that a complex universe could form without a creator, yet you find it 'unreasonable' that this same creator would act to protect the moral complexity and sanctity of human nature from a culture that was literally burning its own children. If He is the creator of the body and the soul, He has the authority to judge both.