For your ammo list, you're missing a location to search, you can just do

inventory * +ammo
this will have it look on all connected grids
inventory {G:My Group} +ammo
this will look in anything which is part of a group named My Group

As for oxygen, simply typing Oxygen will give a readout of all connected air vents, oxygen farms, and average fullness of all oxygen tanks.
There is currently no way of calculating how long oxygen tanks will last.
You can use the same filter styles for Oxygen as with inventory, ie;

Oxygen {G:My Group}
Only gives information about items in the group My Group
Oxygen {Vent}
Only gives information about blocks which have Vent in their name etc