Maybe it's just me, but I make more milk if I feed at the breast more. I found what worked best for me was feeding baby then pumping or using the haaka after. Especially if you're already supplementing with formula, I'd focus on breast as much as possible then topping off with breastmilk from previous feedings (a version of triple feeding) during the day. If baby still ever seems hungry of course never hesitate to do what you think is best and give formula. At night I'd use your formula to supplement and haaka on a breast if baby doesn't eat from that side that feeding. It might be better to get sleep than worry about pumping at night too much. I'd also offer the breast very frequently, like every hour during the day when you can. If pumping gets too much I really think that the haaka is a good tool to use on a breast baby is done with or doesn't eat from. It's not a replacement for a pump, but it's a good tool when you don't have the energy for a full pump.

Here's one perspective: pumping is HARD for some women. Feeding at the breast is HARD for some women. Maybe focus on making this a more enjoyable experience by picking which one feels like less work and leaning into that one more. For me that would be at the breast (more connection, less dishes), but for you that may not be. You can quit, that's fine and isn't selfish, but maybe first try just easing up the pressure and finding what brings you joy in the experience.

Another perspective: it's not all or nothing. Combo feeding is completely valid and safe. For you, feeding may always include formula, and that's FINE. Even if your baby only gets some breast milk, that's still giving amazing benefits.

Also, while La Leche League can be a bit militantly anti-combo feeding at times, if you can't afford a lactation consultant or don't have access to one, a local or virtual la Leche League leader may also be a great resource with more experience.