For now you need to give your vet the benefit of the doubt although I think the dosing methods/instructions have been very questionable. You don't know if the info you relayed the day you had the low readings got conveyed to the vet properly, whether you got his response accurately AND/OR whether the vet could have distracted when responding to the tech/receptionist. This is a prime example of why the vet cannot take on the care of a diabetic cat from arms length. You hold the needle and if anything adverse happens, the vet is free and clear of any guilt because they have no way of knowing if you really followed their instructions or overdoses the cat accidently.
Vets do not get a lot of training on diabetes in school. They also don't usually have a lot of feline diabetics in their practice. Many see more diabetic dogs than cats and treat cats like dogs. Since they often have very few feline patients, they don't stay up to date on current practice which encourages home testing.
I don't think you have to confront the vet. I think you need to make the vet aware of what you are and are not comfortable with and the vet needs to co-operate with you because you are the one who is giving the insulin and having to deal with the outcome.
Unfortunately, what you are describing is all too familiar and time and time again, the caregiver either gets a baptism by fire (hypo or close situation) or the cat manages to keep their BG up but is running in very seriously high numbers because they are in one long continuous bounce. This not only slows down progress but because too much insulin can look identical to too little, it makes it very difficult to get the cat back onto the right path dose wise. I think most vets come around when they see the proof that you know what you are doing and are making good decisions about how much insulin to give.