You're doing fine. Belly aches and the like are pretty common at this age and will probably sort themselves out in a bit. Variability is also to be expected at this age - few newborns have much of a routine.
Honestly, I'd just go with what she wants - in terms of length of feed and frequency. It'll sort itself out.
BTW, 5 hours of sleep = sleeping through for a little baby. So she's doing really well there too.