Oh hun that sucks!
Working as a bookkeeper myself, I know how much attention to detail I do and still I can make mistakes sometimes, but it is very rare and only minor. Luckily you use MYOB and data entry errors are fairly easy to fix - I use Attache which isn't very forgiving but I do love it for that reason as it makes you pay attention to detail IYKWIM. I don't see that your boss would actually be monitoring your work for several hours a day each week, otherwise they wouldn't be doing their job and should be doing yours - which I am sure they wouldn't know how to do nearly good enough . If they are having the same problems with the new accountant, then you know it is all a cop out
Also, with your hubby doing their tax, that can become a tricky situation. Professionally they shouldn't pull the account from him if you were to say something, but that doesn't mean it is the way it will happen. We put on a new staff member a couple of years ago, and then had one of our biggest clients threaten to pull their accounts from us if we didn't let her go because she worked for one of their friends and left that employment under very bad terms. Unfortunately, we had to let her go strictly from a business position (if we'd kept her we would have lost half our workload and there wouldn't have been a position for her anyway, but we still felt really bad about the situation) and then they pulled the accounts from us 6months later to go with an 'internal' position as a cost cutter
I'm sure you are more than competent at your job, sounds like your boss is just trying to push you out, or at least make it difficult for you
Good luck and I hope everything works out for you