Don't know about the rest, but...
1) Rotation lock only locks in landscape. That's normal.
2) Your battery patterns is similar to mine, although mine is also second-hand so not sure how a new battery would fare. Up to 3 weeks of no use, about 5 hours of constant use with display on (e.g. reading e-books) and/or WiFi on (e.g. on Skype).
3) I have kernel-power (v52) and have not noticed any degradation in performance or battery life.