I have been on both ends of the experience of being corrected too much & correcting somebody else too much. Both incidents ended with a short sharp word to each other but no lasting damage to friendship. Its not always easy to keep your mouth shut when you can see so many things wrong, but it best to correct only one or two things and let Nage figure it for themselves or you just end up annoy people.
As for the hand grip well as the expression goes "there is more than one way to skin a cat" So it is possible that it could be a valid way of doing the technique. I've seen alot of differences in hand grips (& techniques) over the years none are really incorrect just some suit my body better than others.
Something to bear in mind is that perhaps he has some problems off the mat. Its not always easy to leave the day to day problems of life behind, he might be having a bad day/week/year.
I believe that either yourself or the other 2 guys would have enough experience to run the Dojo. While your techniques may not be brillant you still know enough to teach the others & should still be able to improve by learning as you teach, or working with each other & discovering things for yourself.
Finally you might want to try and persude a few guest instructors to come down on a regular basis, you never know you might be lucky even if they do live quite far away.
p.s. Do the JKD & BJJ as well !
p.p.s. Out of curosity I just check the Dojo search there are 4 Aikido clubs in Jacksonville maybe you could train at one of the others instead ?