I think you are completely right that actualmente translates better as "nowadays" than "now".
Regarding the examples I think that you are almost right but number four should use ahora.
It will be four years now (since I last saw her). Hará ahora cuatro años (que no la veo o desde la última vez que la vi).
First two should use ahora and three and five are better suited for actualmente but you could use ahora too, and convey the same meaning. Take into account that both actualmente and ahora mean
En el tiempo presente.
