Before I get started on the macro side, as a clicker, you may be more comfortable transitioning to click-casting using an addon like Clique of VuhDo. Where you mouse over the person you want to heal then press a mouse button on their frame to cast spells at them. This would also free up your keybindings for cooldowns and dps spells.
https://www.curseforge.com/wow/addons/clique
https://www.curseforge.com/wow/addons/vuhdo
On to the macro side of things.
@focus can be incorporated into it but due to the help/harm nature of the macro you’ll need to do it with a modifier (ctrl/shift/alt) if you want it to be useful. So I’ll need to know which key you’d like to use for that before I start writing code.
spec is a valid macro condition so you can have it perform different spells for each spec assuming you can fit it all within the 255 character limit (or if you use an addon to extend that limit).
https://us.forums.blizzard.com/en/wow/t/macros-essential-information/21139?u=elvenbane-veknilash