« Last post by Nanashi on Today at 08:52:08 AM »
Merge with Familiar spell. Portable Terrarium/Familiar Bubble blocks LoE. If you can find a way to stop the whole "needs to breath" problem, stick it in extradimensional space. Toughness and belts of con boost its HP as well. If you have the charisma for it you can dip into Bloodrager or Sorcerer and take the Tumor Familiar feat and it can merge with you (gaining fast healing while it does), though how exactly it stacks with other familiars is unclear.
Are you Lawful Neutral? If so take Improved Familiar and take Arbiter as your familiar. It has Pathfinder's version of regeneration, which allows it to have infinite negative HP and get back up (eventually) so long as it isn't hit by anything chaotic (and technically chaotic spells don't count). Backup your spells in a Stone Familiar or (subject to GM approval) have your old familiar become the new one (there's a few cases of this scattered around PF, though it's a bit out of character for arbiters). Egoist a bit weird on compatibility with Improved Familiar, even though it fits so well (there really is an imp on your shoulder telling you to do bad things!), since while it doesn't explicitly lose it most improved familiars have no general bonus.
Figment Familiar is the ultimate in survivability: It returns when you rest. Unfortunately "witch familiars, and familiars that grant spells" can't take it.