The Legendary Pixel Crew

Breath of Life is a fifth level spell. A Cleric needs to be CL 9 to cast it. To create a Use-Activated magic item for a fighter to be the in-combat healer, it's SL x CL x 2000, and x2 if you want it to not take up a magic item slot. In this case, it'd be 9 * 5 * 4000 = 180k gold, or approximately 1/3 what a level 19 character should have, based on the Wealth by Level chart. In this case, it's probably using a hand slot, which would drop it down to 90K, and within the reach of a 12th level character (assuming few, if any, other magic items).

There are also crafter multipliers that can reduce the cost of making items, which is why when my group plays there's always SOMEONE who specializes in gear creation. At the very basic, a -50% cost for making it yourself, which would further reduce the cost to 45 K, within the range for a level 9 character.

Is this hints at... love?

I’m more familiar with 5e but maybe he has something like the Eldritch knight sub class?

He has gloves of first aid.

A much more economical solution than buying gloves that can use that every day, and one hopes that the fighter only occasionally needs to heal anyone.

My guess is that the fighter only has healing abilities so they can revive the cleric... who then heals everyone else.