As a governor myself I'm astounded at quite a few aspects here! How on earth do parents know some of these things? How did the governors tell parents that the head is good at paperwork and managing staff? In a newsletter or is this gossip?
How do parents know that the governors encouraged the old head to retire? Is this gossip as well?
Either a lot of gossip or governors are breaching confidentiality ( for which they can be suspended) or both.
Governors can only act if there is underperformance. Plenty of schools have falling rolls and no money, nothing to do with what head is like. Sadly redundancies, mixed classes etc are getting common and are a direct result of falling rolls and no money but this can all be a vicious circle.
I wonder if old head let things go and now new head is having to sort out the mess.
On complaints, governors they can only act if all other stages of the complaints policy have been done. The policy should be on the website.
It is normal for the head not to give out their email address otherwise they'd be inundated with trivia. School office staff deal with confidential information all the time. I wouldn't let that bit worry you.
There is no category of ofsted that stops you getting outstanding next time. I wonder if you mean the sort that says 'next judgement might not be as good', even so this doesn't prevent getting outstanding even if unlikely.
From a parent viewpoint, I absolutely get what you're saying and it is awful to see a school change like this, but chances of changing anything are remote I'd imagine. Only you can decide whether to move the children but do be aware grass isn't always greener in view of above factors.
Hope things turn out well for your children.