Not sure if this is of any help, im on PS4 controller.
What level are you and how long have you been AST? For me it was just time, seeing what was clunky and adjusting my hot bar accordingly. My most used heals (im right handed) are on the right, my sects and some ogcd on the left as they are used less often. My Oh-SH and insta/raise buttons are 2nd hot bar right handed side, and other random crap on 2nd hotbar left side etc etc. After leveling it for so long you tweak it so you train your brain and hand/eye coordination to make it easier on yourself.
As for healing players, the easy up and down button targets whoever you need. Left and right buttons is to target enemies. I organize party in a row of Me up top. Tank 2nd then 2 dps last. In large groups i'm top as healer, then tank then all the dps and co healer very bottom. Because they usually need less healing or can heal themselves, but also if they get slammed i can save them with one button push (well 2...) i push up which targets them automatically, then Essential Dignity saving them. I'd rather an over heal than a dead co-healer. I DESPISE trying to party with NPC's that keep clumping up and getting in the way when im trying to do a dps dump on AST. I forget the name but that war scene with all the scions it's like UGH MOVE!!! And I don't want to disable target npc because I need to heal npcs in fates sometimes or even other peoples chocos. But yes up and down for players, right button toggles enemies.
Don't even get me started on the card system, there's plenty of threads on that absolute garbage. [EDIT] Also don't worry too much about the wrong card on the wrong person, worry about becoming a fluid healer and comfortable with your moves. It's such a small buff for regular content for only 15sec and dps hardly even notices unless they're "THAT GUY"... Not everyone is pro-neo-astro when they're starting to learn it. Just find a comfortable button slot for you to keep all your card moves in one 4square (cross?) on the hotbar so it's all together, draw, redraw, card sleeve, play etc. Personally I have (all left handed) Redraw (left) Arcana (up) Draw (down) Play (right). Current Ast is indeed a clunk-fest to play optimally. Just do lower level dungeons where you have many of your tool kit that you're comfortable with and tinker around with hotbar (pref not on big pulls lol) to see if you can maximize speed and comfort with your hotbars by swapping junk to the sides and creating an ability flow that speaks to you.
I don't touch macros so I can't help you there. Good luck tho! (^_^)/