Your supply isn't as vulnerable as you think.
If you feed DD when she is hungry - and she seems to have the hang of letting you know.
If you keep an eye on her weight gain and her poos and feed her more often if either of them stop
then you will be fine.

She will have more hungry days and less hungry days, but that is normal.
Getting her to empty one side before having the other is a good thing, and crazy cluster feeding followed by a big sleep is also a good thing.

Have you tried lying down to feed her - with her lying on her side? She may still be a bit tiny, but once she and you get the hang of it it can mean that you can both get a wee nap.

You sound as if you expect your supply to disappear. The only ways that can happen are:
*you get pregnant or take the full contraceptive pill
*you don't feed her often enough (but you definitely are!)
*she can't suck properly (but she's poohing great guns, so you know she can)
*you take pseudoephidrine (but the supply usually comes back)

You are doing really well - he's hoping for another big stretch of sleep for you both tonight!