I would just chuck the batteries personally I have a few crappy 1500mah NiMh's sitting around as paperweights as they are pretty much worthless.
as for a 1500mah lipo honestly that is small persoanlly I would say not to go under 4000mah as that things run time will be extremely short, and potentially could damage the battery.
Battery connectors depends what you like if I had to do it over again I would go EC3 or EC5's(reason I don't is I would have to replace over 30 connectors, and that adds up), but I use Traxxas connectors, others like deans(I personally don't I have tried em in the past). I wouldn't use the airplane connectors as from my experience with airplanes is they pull way less current then ground based RC's and they are not made for the load from the ones I saw (not sure about the ones you listed).
you can pick up 5000mah lipos at hobbyking for like $22