Here are some suggestions:
1. For the icon issue, as I had suggested above, try installing a 3rd party launcher like Nova, which allows you to use one of the multitude of icon packs available on the Play Store (and I'm sure there's at least one that emulates the icons you were used to from Oreo). A 3rd party launcher typically has a ton more customization options that can probably change your experience so that it's closer to what you were used to before.
2. I'm not sure what exactly you mean about fighting to get out a text with the keyboard (is it less accurate now, or have they taken some features away, or something else?), but if you don't like the Samsung keyboard, try any of the many others available on the Play Store, starting with Gboard. Swiftkey is another popular one.
3. Shortened battery life can be due to many many things. Oftentimes, battery drain can increase temporarily after a major system update, which then returns to normal after a few days (i.e., allowing the update to "settle in"). Wiping the cache partition can sometimes help as well:
https://support.t-mobile.com/docs/DOC-37180. (This can also help with other various glitches that can occur after an update, so it's definitely worth a try.)
4. Re: the 2x actions to get from the lockscreen -- are you referring to the need to swipe up first to get to the password entry screen? That's a pretty standard feature that's meant to prevent accidental unlock attempts while the phone is in your pocket or in a bag. If the phone were inadvertently turned on in your pocket and the screen came on immediately to the password screen, additional accidental touches might be interpreted as an unsuccessful unlock attempt -- if that happens a few times, you might find that you've locked yourself out of the phone. You can get around this by using the fingerprint sensor to unlock the phone, or by using Smart Lock (if your phone is usually connected via Bluetooth to something on your person, like a headset or a smartwatch).
5. I'm not sure about the screen going dark and not waking up 30% of the time -- we'd need more details about that. Something like that could be due to an app you installed that might not be playing well with the new update. That kind of thing isn't Samsung's or Google's fault -- the app developer needs to test their apps with the new Android version to make sure it works well (and the dev also needs feedback from users who notice problems).
6. Re: the butt-dialing and accidental sending of photos -- again, would need more details about what's happening there. If you did something to try to get around problem
#4 above (like selecting no lockscreen at all), then if the phone were accidentally being turned on in your pocket and immediately opening to the homescreen, that makes it much easier to accidentally open apps (like the Phone or Camera app) and do things like butt-dial or take random photos of the inside of your pants.
7. It sounds like your Home and Back buttons aren't always responding -- do you have a screen protector on? If so, see if the problem persists with the screen protector off. A poorly designed or poorly fitting screen protector can cause problems with touch detection. Another possibility is that something is causing the phone to lag, which could be a glitch with the system update, but again, could be due to some app not playing well with the update. It might be helpful to see if a lot of these glitches go away in Safe Mode, which temporarily disables all 3rd party apps:
https://support.t-mobile.com/docs/DOC-37190
8. Spelling suggestions are related to the keyboard app. I've heard from others that Samsung Keyboard isn't that great in this respect, so as previously suggested, try a different keyboard app like Gboard.
You might respond, "I shouldn't have to install other apps to do these things", which is understandable -- but this is also one of the strengths of Android, in that you're not limited to what's preinstalled on the phone. Anyway, give those suggestions some consideration. I doubt they'll fix everything to your liking, but hopefully the experience will be a bit more tolerable.