Eleanor has given great advice. Simple things like not putting baby in tight waisted pants is really overlooked (in fact a lot of baby clothing is totally inappropriate for good sleeping etc). Babies used to always be in gowns and, as you say, sleeping positions varied constantly. Also, people lived closer to family so an unsettled baby could be handed around a bit rather than mum and dad being left alone going mental.
A good comfortable baby carrier (eg Ergo) can really help especially when you have another child to care for. Really saves your back.
Lazy boy - we've borrowed one, it has been fab. It is really ugly but I love it, it is my sanity chair

tummy sleeping really helped DD2, but she only liked sleeping upright on me during the day until about 4 months of age, then she was ok in a hammock for day sleeps.I've only just today moved her out of the hammock for day sleeps - she is now on her tummy for day sleeps too (was almost always in her tummy at night) as just would not settle on her back (even hates being on her back during mat time). Both my girls ahve had it, sounds like my mum was a screaming baby and she has reflux as an adult. Strangely me nor my other sibblings were unsettled babies. There is infant reflux on DHs side of the family too but not immediate, showing up in a couple of his cousins kids. It does seem to be more prevalent,I suspect some mild cases are unnecessarily being medicated. We use losec but it aint a magic bullet, you still kind of have to ride out the storm. My eldest hasn't been on losec since 14 months, but I suspect she still has issues with it at times.
I hope she doesn't ahve to deal with it again. It is easier second time around but not really in a way too as you have another child needing your attention too and they all present with it differently.