Okay, so I've been on this website for about 6 years, and I've seen these posts so many times. All I can say, is if you're already wanting to go back to the iPhone because of the keyboard (which is easily replaced), you probably should just do it because deep down I don't think you were ready to leave Apple. I've also watched all of my inlaws do this same thing. They think they're ready for the switch, they go for it, then they realize they aren't ready so they look for silly things to blame it on and act like it was a deal breaker.
I'm honestly not trying to be a jerk, I just can already tell how this one ends, and you could save a lot of time. Briefly looking through, I see that people suggested alternatives and you dislike those too. The Apple keyboard isn't any better, it's just what you're used to. You could get used to any of these too if you wanted to.
EDIT: I may stand corrected this time. I hope Gboard continues to work for you. I do agree that the Samsung keyboard isn't my favorite, but Gboard is great.