These teaching assistants, with little or no experience, are then set about the task of assessing the teachers and advised by the owner to be as critical as possible which is a little disconcerting.

This seems to be an increasingly common set-up at training schools. For anyone considering a job at such an establishment it might be worth asking the question during the interview/courtship stage as to whether the school uses TAs in some or all of there classes and what their role is - they certainly shouldn't be their to observe their peers!

The school itself was built by the previous Director of studies who only recently left, to the detriment of the school

I posted on another thread not long ago that schools often rely on individuals going above and beyond as opposed to an organised system or structure to run the school, it seems that Shane Kunming is another case in point.
As you've alluded to in your helpful post, the school is going through a change of focus which is not supporting the work of the teachers. I'd say this is a common phoneme in many training schools i.e a period where the school provides reasonable conditions to teach and live followed by one where standards fall. Again, it's symptomatic of an organisation without any structure. If you are applying for such positions and basing your decision on prior reputation (positive or negative) it's worth taking into consideration that conditions can and do change sometimes for the better sometimes for the worse.