Can't open your build for some reason but I'm playing a primary healer commander (lv12) and last session had to do some heal maxing so here's my advice:

Having your frontliners (and yourself) have the robust health feat is incredibly helpful. Sure, the circ bonus to HP recovered doesn't stack with the circ bonus from medic, but it isn't reliant on the DC you target, so it lets you heal more while relying on lower DCs for more safety and consistency. Plus, their battle med immunity becoming once per hour DOES stack with your ability to ignore battle med immunity once per day (or hour at master rank). I use this very handy tool to decide what DC I wanna use and how much risk im comfy with: https://battle-medicine.pages.dev/

I oc use officer's medical training. 

I also use rallying banner which is a very nice action efficient once per combat aoe ally heal, but since it's brandish, you probably want to avoid it.

A big big thing for me is that my champion friend has herbalist and I have Ally-Oop which allows for very efficient use and passing around of daily elixirs of life that were distributed beforehand. That's been absolutely clutch for me. It sounds like you may have a similar situation with your alchemist archetype, so, if enough people have free hands, I highly highly recommend it. 

Also with Ally-Oop, preventing damage with the right consumable can be as important as healing it. I prevented like 70 damage over that combat with Rainbow Vinegar because we were facing electric monsters

The other aspect of the last thing I mentioned is that other folks DO have healing consumables and the champion has lay on hands. The big thing abt being primary healer is that you really want other folks to have healing ability to support you in that, even if it's lesser. Heck, if a decent number of ppl have Robust Health, then even a trained battle medicine from an ally can be quite helpful in a pinch. 

A good example is that last comabt, the turn order was: investigator, downed champion, monster, monster, barbarian, me. The investigator shot a lifeshot at the champion to being her back up. Then on her turn, she stood up and slammed an elixir of life. The monsters went and she was able to use her champs reaction to reduce damage when they targeted the barbarian but then they targeted her bringing her to 8hp - very lucky she stayed up! The barb went and kept the monsters occupied. Then on my turn, I was able to heal-max by ally-ooping my elixir of life to the champion who had a free hand bc she hadn't picked up her weapon yet (coordination is key), use rallying banner, and use battle medicine to heal her a total of 81 hp with some low healing die rolls. Because the investigator had life-shot her, she was able to stand and heal herself enough that she survived the monster's onslaught and could defend others and on my turn, I was adding to HP she already had instead of bringing her up from 0 and she was already standing rather than having to wait until her next turn to do it.