You asked three questions and I have the answer to the first two. At least the way I do it.
For #1 and #2 I use the AOD.(always on display) You turn it on and set it up from Settings: Display: AOD. Tap on AOD. That will open the configuration page. First, pick the AOD you want and customize it however you like. The last one has the photo. But you won't get the bubbles. Each one is different so try them all until you find what you want.
Second, turn on "Quick tools and music player". Then, when you lock your phone, the AOD will appear. Under the date there will be a line with notification icons like the notification bar on your phone. Swipe that line left or right and you'll get different things. One will be a bunch of tools, one of which is the flashlight.
#3. I don't use swipe typing however you can change the settings of the default LG keyboard to turn on Path Input, if thats what you mean.
You have to be using an app with a keyboard. The LG keyboard has a line of icons on the top. Tap the gear for Settings. Then you'll see the above page and turn on Path Input. If that isn't what you want, then you may have to use a downloaded keyboard.

Good luck

 

2) As far as customizing messaging, for years I have been using the Chomp app. The pro version is only $1.99. I has many features that you are looking for and more.

 

As to question #1 - you can also símply add a shortcut to the lock screen in settings.

#2 - I'm using Textra with a app provided dark background.
¯\_(ツ)_/¯

#3 If - you Gboard, you can set glide typing in the app settings.