Great looking board!
If you don't mind my asking, what is the SMD LDO regulator you're using with 900nA idle current? Any information on what it does over the 0.0 ~ 3.x+ voltage range?
I currently have Microchip's MCP1700T (3.3V) regulator spec'd for my 'Draculino
' energyharvesting board. It's comparable in Iq (1.3uA) above 3.3V, but gets a little wonky if the input voltage drops below the regulator's nominal output voltage. (Yeah yeah, it's never supposed to be below that, but...) Characterizing over the 0 ~ 6V input range reveals:
Not unacceptable, but if another part may perform better I'm for trying it out!
* don't ask what it does in reverse bias! The pile of reversed FETs all over the power supply are there for a reason