Familiars aren't going to be affected by anything dealing with your spell focus. Skeleton, like all Undead summons, will benefit from
Negative Energy Burst, but I believe we've removed the save from it when it's rolled to heal an allied undead. So it doesn't really matter if you boost your Necromancy DC there, regarding your familiar at least.
Epic Necromancy Focus will
extend the duration of the Pharaoh Sentinel. Epic Conjuration is used for Magical Beast, Outsider, and EDK.
The Build Forum is going to be the better place for questions like this.