Yes all of your allies must come from the same era EA. Similarly ISA's allies, must all come from the same race.
I don't see why you couldn't buy fighter upgrades, as long as that patrol point comes from your allies FAP allocation, and of course you stick to the correct era (no Firebolts on an Avenger!). So your 2 battle points could buy an Omega filled with Firebolts, a Delphi, Chronos and a Myrmidon.
I don't see why you couldn't buy fighter upgrades, as long as that patrol point comes from your allies FAP allocation, and of course you stick to the correct era (no Firebolts on an Avenger!). So your 2 battle points could buy an Omega filled with Firebolts, a Delphi, Chronos and a Myrmidon.