I tell ya, husband support is so vital to feeling like you can keep breastfeeding/pumping, and therefore being able to!
What your daughter gains with breastmilk is a lot of things, actually, including the perfect food, as well as your immunities. And these things don't stop when the baby turns 1 y/o, so I think it'd be great if you could keep it up even longer. The more breastmilk and the less formula, the better.
That said, I know that pumping can be a drain (no pun intended). ;-) I'm a SAHM, but I pumped for a friend's adopted baby for a few weeks, so I know some of what has to happen -- and I didn't even have to figure out work and "dropping off the baby" schedules, so kudos to you for making it work this long!
*Must* you make a decision? Can you just keep pumping, accepting that you're getting lower production but still keeping on as you have been, or perhaps dropping one pumping session per day, and just see how long it lasts?
You sound like your mind is already made up, and you just want people to agree with you and say, "It's all good." I'm not going to try arguing you out of your decision, although I still give a vote of "keep on pumping."
It sounds like at some point your daughter will get formula, unless you can keep up with exclusive breastmilk until she's a year old, when straight cow's milk won't hurt her stomach (or ignore the milk and formula, and just switch to table food, water, and occasional juice). If you want her to take it, you can probably add it in slowly -- say, start off with 1/2 oz or 1 oz of formula per bottle of breastmilk, and gradually increase the proportion. That way, she gets used to the different taste and consistency slowly, and will be more likely to take 100% formula.