Easyest class to use for healer

[Erakir]

WHM is a cruddy healer early on, it's true - but going single pull to single pull it's gonna be fine and bots have long gotten through parties with medica spam. It's only compared to others that WHM comes up obviously short pre-50, but I think medica/medica2 spam alone will make it very functional for this situation. It's powerful for someone to have a multi-purpose healing option that doesn't require targeting in this case and will function well all through 80. While fairy does a lot without anything at all, I think M2 will ultimately carry further mostly due to succor's functionality, and being able to put a regen macro in place would do a ton for tank healing too. Both jobs would likely be fine though.

I'd like to add a suggestion for this more unique circumstance:

For whichever job is selected, consider adding Lucid Dreaming to a DoT macro. Or a regen macro if you go with WHM. For instance if using the aero macro posted earlier-

/micon "Aero"
/merror off
/ac "Aero" <t>
/ac "Aero" <tt>
/wait 1
/ac "Lucid Dreaming"

It's one less thing he'll have to keep track of that healers do need to press semi-frequently. Could do the same with things like aetherflow or thin air if he's having difficulty with them.
Sure, it's not ideal to be pressing it like that at all, but if we're trying to eliminate button presses I think it could help. It's a CD he won't need to pay attention to.

You may want to consider doing this with other abilities too, such as assize or divine benison. With a /wait of 2 they should be able to activate after a Cure and possibly Cure 2.
For benison in particular, I'd suggest
/ac "Divine Benison" <2> so it's always going on the tank (if default party sorting)

None of these outside of lucid will really be needed for what you're describing, but there won't be any real harm throwing them in the macros and it'll only make him stronger than not pressing them at all, all without needing any extra attention from him.

I think you could get by with a 5ish button healer this way via cure/cure2/medica (replace with m2 later)/stone macro/DoT macro.

Could even combine DoT/Regen into one macro if you feel like it and are going WHM:
/micon "Regen"
/merror off
/ac "Regen" <2>
/wait 1
/ac "Lucid Dreaming"
/wait 2
/ac "Aero" <t>
/ac "Aero" <tt>
/wait 1
/ac "Some other oGCD" <2>

That should be a 3s wait so both GCDs should activate - Regen on the tank then Aero on his target or target's target. Tell him to press it now and then (every 30s) and it might work well for him?

Another I'd consider putting off to the side: A swiftcast/wait/raise macro:
/micon "Swiftcast"
/merror off
/ac "Swiftcast"
/wait 1
/ac "Raise" <2>
/ac "Raise" <3>
/ac "Raise" <4>
(Through 8 if needed for 8m content)
(Also replace Raise with whichever resurrection spell is used)
It's been awhile since I've dealt with macro nuances but I think that one should raise the first dead person in the party list without timing/error issues. Make it big, make it obvious, let him know if he ever sees someone dead, press that one.

Depending on how he plays, it could be worth separating hotbars so one is for healing and one is for any damage macros. If he clicks, having a clear visual separation could help? Depends on how he goes about things, and you'll know far more than any of us there.
Edit: Oh, just saw you say he plays with controller, my bad

Edit: I also suggest one of you may want to play bard alongside. Warden's Paean can be used to cover some of the harsher debuffs if Esuna ends up difficult for him, particularly if he finds himself silenced or 30s paralyzed. Or you can echo drops/spine drops him - it's just Warden's is ranged, potions aren't.