i used dbpro for a few years then stopped coding altogether for a few years before i picked up AppGameKit (a few years ago). there was a transition/learning (unlearning)-curve that seemed pretty sharp which is what you're experiencing now before AppGameKit became more natural.
leading up to AppGameKit, i read (every single) post in AppGameKit Chat and got a pretty good feel for how i should go about doing things and there were a few posts similar to yours here re: migrating from DBPro to AppGameKit but nothing like a transition guide. i remember a couple years ago a DBPro user came to AppGameKit and spoke about writing one which never happened...
1 thing that took some getting used to was the fact that there are no spaces in the AppGameKit commands so i use a couple versions of "camel case" to keep my code readable. that helped me a lot where i don't believe i did that with DBPro.
meanwhile, to your direct coding questions:
1)
CLS: see
ClearScreen() and
SetClearColor().
2)
wait key: see
THIS SNIPPET which is the closest functionality that i've seen. with that, don't forget a big difference between DBPro and AppGameKit is that AppGameKit is meant to be 1) written on different OSs and 2) exported to different platforms and especially mobile where there really won't be a strict "wait key" notion. instead, we have things like the snippet and notions of:
Repeat
...
Sync()
Until
GetPointerPressed()
with that, you'll notice that AppGameKit tries (pretty hard and pretty successfully) to be "all encompassing" from a Desktop & Mobile perspective while you will discover some scenarios fall short (where you'll need to take advantage of the more than 1,500 commands (i believe?) to create the functionality that you might have been accustomed to in (a strictly-Windows) DBpro (single command) scenario.
3a)
set cursor (x,y): AppGameKit has basic
Print and PrintC (etc) functionality but no SetCursor(). instead, AppGameKit has a
Text command set that is 10 times more robust than a "simple" Print command set that you are accustomed to coming from DBPro (which is pretty much used in a light "debug" manner for me until i'm ready to flesh out a set of Text Objects for a given project).
3b)
ink: see
SetPrintColor()
4) "have the editor NOT indent the coding": from within the Studio IDE, see Edit/Preferences then
Enable Auto Indentation and
Enable Smart Indentaion.
otherwise, i recommend skimming through
all the command sets. you'll be able to connect some dots when it comes to DBPro vs AGK; it should also help getting your mind into "the AppGameKit lane", in general.
i'd also skim through some of the meatier posts on a given topic that might interest you, look at some of the [AGK]-tagged
Code Snippets (including mine; link found in my sig), to see how some of us have been "doing things" while also being bite-sized real/working code examples (also found in the online docs for many commands (ie, see the user example for
CreateText() ).
that should be enough to help get you into the thick of things. and, i hope it helps!
unfortunately, i believe i've forotten ANYTHING i might have known in DBPro so i'm no help with a transition guide. perhaps it's something you could do at some point? (take notes! (or, not

) ).
otherwise, as you have more questions, feel free to post. with that, i do recommend using the AppGameKit Discord server for a sometimes quicker response or just general chat. invite link found near the top of the first post
HERE.
btw, while i mentioned a sharp learning curve for me, thankfully it wasn't a monstrous,
sweeping curve. i was back on the straightaway before i knew it... and never looked back.