Great questions! I think it's great that you're not doing much supplementing anymore. Remember babies can be fussy for many reasons so I wouldn't use the bottle as your go-to solution for fussiness. First option is the breast, if that doesn't do it, try a dim room, motion (rocking, bouncing on an exercise ball, walking baby around in your arms, a carrier or a stroller), soft singing.
Baby will not need bigger bottles or more food as the year progresses - milk intake is stable between 1 month and 1 year. Nor will she need less. Solids before age one is for learning new tastes, textures and the motor skills to self-feed; breastmilk remains the primary source of nutrition. So yes, she will still need to eat at the same frequency even once she starts sampling solids, and bottle sizes should also remain about the same. Because she does need the same frequency of feedings, a lot of moms will continue to co-sleep, if for no other reason than it makes it less tiring to be nursing baby at night! It's sort of a myth that co-sleeping is going to make baby a "bad sleeper" later on, personally that has not been my experience.
Whether it's sufficient to nurse/pump every 3 hours during the day, I think you just have to see how things go. If baby is gaining weight (indicating your supply is fine) and you have stable pump output, then you know it's fine. If you're starting to have less pump output, that might be a signal you need to do more.
It's true that it's hard to keep track of how many times in 24 hours if you are cluster feeding. Nor do you necessarily need to be that compulsive about keeping track. If you are cluster nursing in the evening and nursing several times overnight, and nursing once in the day and baby gets a few bottles, it sounds like she is getting the frequency she needs. Every 3 hours for the bottle may be about right, sometimes they may be a little closer together, sometimes a little farther apart (if she takes a long nap for example).